1.1.1 A Word on GNU

The Linux kernel project began as a solo endeavor by Linus Torvalds in 1991, but as Isaac Newton once said, “If I have seen further, it is by standing on the shoulders of giants.” When Linus Torvalds began the kernel the Free Software Foundation had already established the idea of collaborative software. They entitled their effort GNU, a recursive acronym that means simply “GNU's Not Unix”. GNU software ran atop the Linux kernel from day 1. Their compiler gcc was used to compile the kernel. Today many GNU tools from gcc to gnutar are still at the basis of every major Linux distribution. For this reason many of the Free Software Foundation's proponents fervently state that their work should be given the same credit as the Linux kernel. They strongly suggest that all Linux distributions should refer to themselves as GNU/Linux distributions.

This is the topic of many flamewars, surpassed only by the ancient vi versus emacs holy war. The purpose of this book is not to fan the fires of this heated discussion, but rather to clarify the terminology for neophytes. When one sees GNU/Linux it means a Linux distribution. When one sees Linux they can either be referring to the kernel, or to a distribution. It can be rather confusing. Typically the term GNU/Linux isn't used because it's a mouth full.

2.1.1 man

The man command (short for “manual”) is the traditional form of online documentation in Unix and Linux operating systems. Comprised of specially formatted files, the “man pages”, are written for the vast majority of commands and are distributed with the software itself. Executing man somecommand will display the man page for (naturally) the command specified, in our example this would be the imaginary program somecommand.

As you might imagine, the amount of man pages can quickly add up, becoming overly confusing and seriously complicated, even for an advanced user. So, for this reason, man pages are grouped into enumerated sections. This system has been around for a very long time; enough so that you will often see commands, programs, and even programming library functions referred to with their man section number.

For example:

You might see a reference to man(1). The numbering tells you that “man” is documented in section 1 (user commands); you can specify that you want the section 1 man page for “man” with the command man 1 man. Specifying the section that man should look in is useful in the case of multiple items with the same name.

In addition to man(1), there are the commands whatis(1) and apropos(1) available to you, whose shared purpose is to make it easier to find information in the man system.

The command whatis gives a very brief description of system commands, somewhat in the style of a pocket command reference.

Example:

% whatis whatis
whatis (1)  - search the whatis database for complete words

The command apropos is used to search for a man page containing a given keyword.

Example:

% apropos wav
cdda2wav    (1)  - a sampling utility that dumps CD audio data into wav sound files
netwave_cs  (4)  - Xircom Creditcard Netwave device driver
oggdec      (1)  - simple decoder, Ogg Vorbis file to PCM audio file (WAV or RAW)
wavelan     (4)  - AT&T GIS WaveLAN ISA device driver
wavelan_cs  (4)  - AT&T GIS WaveLAN PCMCIA device driver
wvlan_cs    (4)  - Lucent WaveLAN/IEEE 802.11 device driver

If you'd like further information on any of these commands, read their man pages for the details. ;)

2.1.2 The /usr/doc Directory

The source for most packages that we build comes with some sort of documentation: README files, usage instructions, license files, etc. Any sort of documentation that comes with the source is included and installed on your system in the /usr/doc directory. Each program will (usually) install its own documentation in the order of:

/usr/doc/$program-$version

Where $program is the name of the program you are wanting to read about, and $version is (obviously) the appropriate version of software package installed on your system.

For example, to read the documentation for the command man(1) you would want to cd to:

% cd /usr/doc/man-$version

If reading the appropriate man page(s) doesn't provide you with enough information, or address what you're looking for in particular, the /usr/doc directory should be your next stop.

2.1.3 HOWTOs and mini-HOWTOs

It is in the truest spirit of the Open Source community that brings us to the HOWTO/mini-HOWTO collection. These files are exactly what they sound like - documents and guides describing how to do stuff. If you installed the HOWTO collection, the HOWTOs will be installed to /usr/doc/Linux-HOWTOs and the mini-HOWTOs to /usr/doc/Linux-mini-HOWTOs.

Also included in the same package series is a collection of FAQs, which is an acronym which stands for

These documents are written in a “Question and answer” style for (surprise) Frequently Asked Questions. The FAQs can often be a very useful place to look if you're just looking for a “Quick Fix” to something. If you decide to install the FAQs during setup, you will find them installed to the /usr/doc/Linux-FAQs directory.

These files are well worth reading whenever you're not quite sure how to proceed with something. They cover an amazing range of topics, more often than not in a surprisingly detailed manner. Good stuff!

2.2.1 The Official Website and Help Forums

The Official Slackware Website

The Official Slackware Linux website is sometimes out of date, but still contains information relevant to the latest Slackware versions. At one time an active help forum existed there before a horde of trolls, troublemakers, and whiners descended on the forum. Maintaining the forum was beginning to be too much work, and so Pat shut it down. One can find that old forum back up and running complete with searchable archives of the old data at http://www.userlocal.com/phorum/.

After the forums were taken down on http://slackware.com, several other sites sprang up that offered forum support for Slackware. After much thought, Pat chose to endorse www.linuxquestions.org as the official forum for Slackware Linux.

2.2.2 E-mail Support

Everyone who purchases an official CD set is entitled to free installation support via e-mail from the developer. That having been said, please keep in mind that we, the developers, (and a vast majority of users) of Slackware are of “The Old School”. That means that we prefer to help those who have a sincere interest and are willing to help themselves in the process. We will always do our best to help everyone who emails us with support questions. However, Please check your documentation and the website (especially the FAQs and maybe some of the forums listed below) before e-mailing. You may get a faster answer that way, and the less e-mail we have to answer, obviously the sooner we will be of assistance to those that need it.

The e-mail address for technical support is: support@slackware.com. Other e-mail addresses and contact information are listed on the website.

2.2.3 Non-Official Websites and Help Forums

3.1.1 The Official Disc and Box Sets

The official Slackware Linux CD set is available from Slackware Linux, Inc. The CD set consists of 4 discs. The first disk contains all the software needed for a basic server install, and the X window system. The second cd is a “live” cd; that is, a bootable cd that installs into RAM and gives you a temporary installation to play around with or do a data or machine rescue. This cd also contains a few packages such as the KDE and GNOME desktop environments. A few other goodies are included on the second cd including many non-vital packages in the “extra” folder. The third and fourth CDs contain the source code to all of Slackware, along with the original edition of this book.

One may also purchase a boxed set that includes the 4 discs and a copy of this book, as well as lots of neat Slackware gear to show off your geek pride. CD subscriptions are available at a reduced rate also.

The preferred method for shopping for Slackware merchandise is online at the Slackware store.

http://store.slackware.com

You can also call or e-mail your order in.

3.1.2 Via the Internet

Slackware Linux is also freely available over the Internet. You may email in your support questions, but higher priority will be given to those who have purchased the official CD set. With that said, we get a lot of e-mails and our time is rather limited. Before e-mailing for support consider reading Chapter 2 first.

The official Slackware Linux Project website is located at:

http://www.slackware.com/

The primary FTP location for Slackware Linux is:

ftp://ftp.slackware.com/pub/slackware/

Bear in mind that our ftp site, while open for general use, does not have unlimited bandwidth. Please consider using a mirror near you to download Slackware. An incomplete list of mirrors can be found on our site at http://www.slackware.com/getslack.

3.2.1 The Software Series

For reasons of simplicity, Slackware has historically been divided into software series. Once called “disk sets” because they were designed for floppy-based installation, the software series are now used primarily to categorize the packages included in Slackware. Today, floppy installation is no longer possible.

The following is a brief description of each software series.

3.2.2 Installation Methods

3.2.3 Boot Disk

The boot disk is the floppy you actually boot from to begin the installation. It contains a compressed kernel image which is used to control the hardware during installation. Therefore, it is very much required (unless you're booting from CD, as is discussed in the section called CD-ROM). The boot disks are located in the bootdisks/ directory in the distribution tree.

There are more Slackware boot disks than you can shake a stick at (which is to say about 16). A complete list of boot disks, with a description of each, is available in the Slackware distribution tree in the file bootdisks/README.TXT. However, most people are able to use the bare.i (for IDE devices) or scsi.s (for SCSI devices) boot disk image.

See Section 3.2.6 for instructions on making a disk from an image.

After booting, you will be prompted to insert the root disk. We recommend that you just humor the boot disk and play along.

3.2.4 Root Disk

The root disks contain the setup program and a filesystem which is used during installation. They are also required. The root disk images are located in the directory rootdisks in the distribution tree. You'll have to make two root disks from the install.1 and install.2 images. Here you can also find the network.dsk, pcmcia.dsk, rescue.dsk, and sbootmgr.dsk disks.

3.2.5 Supplemental Disk

A supplemental disk is needed if you are performing an NFS install or installing to a system with PCMCIA devices. Supplemental disks are in the rootdsks directory in the distribution tree, with the filenames network.dsk and pcmcia.dsk. Recently other supplemental disks such as rescue.dsk and sbootmgr.dsk have been added. The rescue disk is a small floppy root image that runs in a 4MB RAM drive. It includes some basic networking utilities and the vi editor for quick fixes on busted machines. The sbootmgr.dsk disk is used to boot other devices. Boot off this disk if your bootable CD-ROM drive doesn't want to boot the Slackware CDs. It will prompt you for different things to boot and may offer a convenient way to work around a buggy BIOS.

The root disk will instruct you on the use of supplemental disks when it is loaded.

3.2.6 Making the Disks

Once you've selected a boot disk image, you need to put it on a floppy. The process is slightly different depending on which operating system you're using to make the disks. If you're running Linux (or pretty much any Unix-like OS) you'll need to use the dd(1) command. Assuming bare.i is your disk image file and your floppy drive is /dev/fd0, the command to make a bare.i floppy is:

% dd if=bare.i of=/dev/fd0

If you're running a Microsoft OS, you'll need to use the RAWRITE.EXE program, which is included in the distribution tree in the same directories as the floppy images. Again assuming that bare.i is your disk image file and your floppy drive is A:, open a DOS prompt and type the following:

C:\ rawrite a: bare.i

3.4.1 HELP

If this is your first time installing Slackware, you might want to take a look at the help screen. It will give a description of each part of setup (much like the one we're writing now, but less involved) and instructions for navigating the rest of the install.

3.4.2 KEYMAP

If you require a keymap other than the United States “qwerty” layout, you may want to take a look at this section. It offers a number of alternate layouts for your keyboarding enjoyment.

3.4.3 ADDSWAP

If you created a swap partition (back in Section 3.3), this section will allow you to enable it. It will autodetect and display the swap partitions on your hard drive, allowing you to select one to format and enable.

3.4.4 TARGET

The target section is where your other (non-swap) partitions are formatted and mapped to filesystem mount points. A list of the partitions on your hard disk will be displayed. For each partition, you will be given the option of whether to format that partition or not. Depending on the kernel used, you can choose between reiserfs (the default), ext3, ext2, jfs, and xfs. Most people use either reiserfs or ext3. In the near future we may see support for reiserfs4 slip in.

The first option in the target section is the selection of a partition on which to install your root (/) filesystem. After that, you will be able to map other partitions to filesystems as you choose. (For instance, you may want your third partition, say /dev/hda3, to be your home filesystem. This is just an example; map the partitions as you see fit.)

3.4.5 SOURCE

The source section is where you select the source media from which you are installing Slackware. Currently there are four sources to choose from. These are CD-ROM, NFS, or a premounted directory.

The CD-ROM selection enables a CD-ROM based installation. It will offer the option of scanning for a CD-ROM drive or displaying a list from which you can pick your drive type. Make sure you have the Slackware CD in your drive before allowing it to scan.

The NFS selection prompts for your network information and the network information for your NFS server. The NFS server must be set up in advance. Also note that you cannot use hostnames, you must use the IP addresses for both your machine and the NFS server (there is no name resolver on the setup disk). Naturally you must have used the network.dsk floppy to add support for your network controller.

The premounted directory offers the most flexibility. You can use this method to install from things such as Jaz disks, NFS mounts over PLIP, and FAT filesystems. Mount the filesystem to a location of your choosing before running setup, then specify that location here.

3.4.6 SELECT

The select option allows you to select the software series that you wish to install. These series are described in Section 3.2.1. Please note that you must install the A series to have a working base system. All other series are optional.

3.4.7 INSTALL

Assuming that you have gone through the “target”, “source”, and “select” options, the install option will allow you to select packages from your chosen software series. If not, it will prompt you to go back and complete the other sections of the setup program. This option allows you to select from six different installation methods: full, newbie, menu, expert, custom, and tag path.

The full option will install every package from all the software series that you chose in the “select” section. There is no further prompting. This is the easiest installation method, since you do not need to make any decisions on the actual packages to install. Of course, this option also takes up the most hard drive space.

The next option is newbie. This option installs all of the required packages in the selected series. For all other packages, it offers a prompt where you can select “Yes”, “No”, or “Skip”. Yes and No do the obvious, while Skip will go ahead to the next software series. Additionally, you will see a description and size requirement for each package to help you decide if you need it. We recommend this option for new users, as it ensures that you get all the required packages installed. However, it is a little slow because of the prompting.

Menu is a faster and more advanced version of the newbie option. For each series, a menu is displayed, from which you can select all the non-required packages you want to install. Required packages are not displayed on this menu.

For the more advanced user, install offers the expert option. This allows you complete control over what packages get installed. You can deselect packages that are absolutely required, resulting in a broken system. On the other hand, you can control exactly what goes onto your system. Simply select the packages from each series that you want installed. This is not recommended for the new user, as it is quite easy to shoot yourself in the foot.

The custom and tag path options are also for advanced users. These options allow you to install based upon custom tag files that you created in the distribution tree. This is useful for installing to large numbers of machines fairly quickly. For more information on using tag files, see Section 18.4.

After selecting your installation method, one of a few things will happen. If you selected full or menu, a menu screen will appear, allowing you to select the packages to be installed. If you selected full, packages will immediately start getting installed to the target. If you selected newbie, packages will be installed until an optional package is reached.

Note that it is possible to run out of space while installing. If you selected too many packages for the amount of free space on the target device, you will have problems. The safest thing to do is to select some software and add more later, if you need it. This can easily be done using Slackware's package management tools. For this information, see Chapter 18.

3.4.8 CONFIGURE

The configure section allows you to do some basic system configuration, now that the packages have been installed. What you see here depends in large part upon which software you have installed. You will, however, always see the following:

4.1.1 File System Layout

The first noticeable difference between Slackware Linux and a DOS or Windows system is the filesystem. For starters, we do not use drive letters to denote different partitions. Under Linux, there is one main directory. You can relate this to the C: drive under DOS. Each partition on your system is mounted to a directory on the main directory. It's kind of like an ever-expanding hard disk.

We call the main directory the root directory, and it's denoted with a single slash (/). This concept may seem strange, but it actually makes life easy for you when you want to add more space. For example, let's say you run out of space on the drive that has /home on it. Most people install Slackware and make one big root drive. Well, since a partition can be mounted to any directory, you can simply go to the store and pick up a new hard drive and mount it to /home. You've now grafted on some more space to your system. And all without having to move many things around.

Below, you will find descriptions of the major top level directories under Slackware.

You should now have a good feel for which directories contain what on the filesystem. More detailed information about the filesystem layout is available in the hier(7) man page. The next section will help you find specific files easily, so you don't have to do it by hand.

4.1.2 Finding Files

You now know what each major directory holds, but it still doesn't really help you find things. I mean, you could go looking through directories, but there are quicker ways. There are four main file search commands available in Slackware.

%  which bash
/bin/bash

%  whereis bash
bash: /bin/bash /usr/bin/bash /usr/man/man1/bash.1.gz

%  find / -name xinitrc
/var/X11R6/lib/xinit/xinitrc

%  slocate xinitrc   # we don't have to go to the root
/var/X11R6/lib/xinit/xinitrc
/var/X11R6/lib/xinit/xinitrc.fvwm2
/var/X11R6/lib/xinit/xinitrc.openwin
/var/X11R6/lib/xinit/xinitrc.twm

4.1.3 The /etc/rc.d Directory

The system initialization files are stored in the /etc/rc.d directory. Slackware uses the BSD-style layout for its initialization files as opposed to System V init scripts, which tend to make configuration changes much more difficult without using a program specifically designed for that purpose. In BSD-init scripts, each runlevel is given a single rc file. In System V, each runlevel is given its own directory, each containing numerous init scripts. This provides an organized structure that is easy to maintain.

There are several categories of initialization files. These are system startup, runlevels, network initialization, and System V compatibility. As per tradition, we'll lump everything else into another category.

4.2.1 The /kernels Directory on the Slackware CD-ROM

The precompiled Slackware kernels are available in the /kernels directory on the Slackware CD-ROM or on the FTP site in the main Slackware directory. The available kernels change as new releases are made, so the documentation in that directory is always the authoritative source. The /kernels directory has subdirectories for each kernel available. The subdirectories have the same name as their accompanying boot disk. In each subdirectory you will find the following files:

To use a kernel, copy the System.map and config files to your /boot directory and copy the kernel image to /boot/vmlinuz. Run /sbin/lilo(8) to install LILO for the new kernel, and then reboot your system. That's all there is to installing a new kernel.

The kernels that end with a .i are IDE kernels. That is, they include no SCSI support in the base kernel. The kernels that end with .s are SCSI kernels. They include all the IDE support in .i kernels, plus SCSI support.

4.2.2 Compiling a Kernel from Source

The question “Should I compile a kernel for my system?” is often asked by new users. The answer is a definite maybe. There are few instances where you will need to compile a kernel specific to your system. Most users can use a precompiled kernel and the loadable kernel modules to achieve a fully working system. You will want to compile a kernel for your system if you are upgrading kernel versions to one that we do not currently offer in Slackware, or if you have patched the kernel source to get special device support that is not in the native kernel source. Anyone with an SMP system will definitely want to compile a kernel with SMP support. Also, many users find a custom compiled kernel runs much faster on their machine. You may find it useful to compile the kernel with optimizations for the specific processor in your machine.

Building your own kernel is not that hard. The first step is to make sure you have the kernel source installed on your system. Make sure that you installed the packages from the K series during the installation. You will also want to make sure you have the D series installed, specifically the C compiler, GNU make, and GNU binutils. In general, it's a good idea to have the entire D series installed if you plan on doing any kind of development. You can also download the latest kernel source from http://www.kernel.org/mirrors.

% su -
Password:
# cd /usr/src/linux

# make mrproper

# make config           (text-based Q&A version)
# make menuconfig       (menu driven, text-based version)
# make xconfig          (X-based version, make sure you are in X first)

# make dep
# make clean

# make bzImage

# make modules

# mv /boot/vmlinuz /boot/vmlinuz.old
# cat arch/i386/boot/bzImage > /vmlinuz
# mv /boot/System.map /boot/System.map.old
# cp System.map /boot/System.map
# make modules_install

# make bzImage V=1

4.2.3 Using Kernel Modules

Kernel modules are another name for device drivers that can be inserted into a running kernel. They allow you to extend the hardware supported by your kernel without needing to pick another kernel or compile one yourself.

Modules can also be loaded and unloaded at any time, even when the system is running. This makes upgrading specific drivers easy for system administrators. A new module can be compiled, the old one removed, and the new one loaded, all without rebooting the machine.

Modules are stored in the /lib/modules/kernel version directory on your system. They can be loaded at boot time through the rc.modules file. This file is very well commented and offers examples for major hardware components. To see a list of modules that are currently active, use the lsmod(1) command:

# lsmod
Module                  Size  Used by
parport_pc              7220   0 
parport                 7844   0  [parport_pc]

You can see here that I only have the parallel port module loaded. To remove a module, you use the rmmod(1) command. Modules can be loaded by the modprobe(1) or insmod(1) command. modprobe is usually safer because it will load any modules that the one you're trying to load depends on.

A lot of users never have to load or unload modules by hand. They use the kernel autoloader for module management. By default, Slackware includes kmod in its kernels. kmod is a kernel option that enables the kernel to automatically load modules as they are requested. For more information on kmod and how it is configured, see /usr/src/linux/Documentation/kmod.txt. You'll have needed to have the kernel source package, or downloaded kernel source from http://kernel.org.

More information can be found in the man pages for each of these commands, plus the rc.modules file.

5.2.1 Loading Network Modules

Kernel modules that are to be loaded on boot-up are loaded from the rc.modules file in /etc/rc.d or by the kernel's auto module loading started by /etc/rc.d/rc.hotplug. The default rc.modules file includes a Network device support section. If you open rc.modules and look for that section, you'll notice that it first checks for an executable rc.netdevice file in /etc/rc.d/. This script is created if setup successfully autoprobes your network device during installation.

Below that “if” block is a list of network devices and modprobe lines, each commented out. Find your device and uncomment the corresponding modprobe line, then save the file. Running rc.modules as root should now load your network device driver (as well as any other modules that are listed and uncommented). Note that some modules (such as the ne2000 driver) require parameters; make sure you select the correct line.

5.2.2 LAN (10/100/1000Base-T and Base-2) cards

This heading encompasses all of the internal PCI and ISA networking cards. Drivers for these cards are provided via loadable kernel modules as covered in the previous paragraph. /sbin/netconfig should have probed for your card and successfully set up your rc.netdevice file. If this did not occur, the most likely problem would be that the module that you're attempting to load for a given card is incorrect (it is not unheard of for different generations of the same brand of card from the same manufacturer to require different modules). If you are certain that the module that you're attempting to load is the correct one, your next best bet would be to refer to the documentation for the module in an attempt to discover whether or not specific parameters are required during when the module is initialized.

5.2.3 Modems

Like LAN cards, modems can come with various bus support options. Until recently, most modems were 8 or 16 bit ISA cards. With the efforts of Intel and motherboard manufacturers everywhere to finally kill off the ISA bus completely, it is common now to find that most modems are either external modems that connect to a serial or USB port or are internal PCI modems. If you wish for your modem to work with Linux, it is VITALLY important to research your prospective modem purchase, particularly if you are considering purchasing a PCI modem. Many, if not most, PCI modems available on store shelves these days are WinModems. WinModems lack some basic hardware on the modem card itself: the functions performed by this hardware are typically offloaded onto the CPU by the modem driver and the Windows operating system. This means that they do not have the standard serial interface that PPPD will be expecting to see when you try to dial out to your Internet Service Provider.

If you want to be absolutely sure that the modem you're purchasing will work with Linux, purchase an external hardware modem that connects to the serial port on your PC. These are guaranteed to work better and be less trouble to install and maintain, though they require external power and tend to cost more.

There are several web sites that provide drivers and assistance for configuring WinModem based devices. Some users have reported success configuring and installing drivers for the various winmodems, including Lucent, Conexant, and Rockwell chipsets. As the required software for these devices is not an included part of Slackware, and varies from driver to driver, we will not go into detail on them.

5.2.4 PCMCIA

As part of your Slackware install, you are given the opportunity to install the pcmcia package (in the “A” series of packages). This package contains the applications and setup files required to work with PCMCIA cards under Slackware. It is important to note that the pcmcia package only installs the generic software required to work with PCMCIA cards under Slackware. It does NOT install any drivers or modules. The available modules and drivers will be in the /lib/modules/`uname -r`/pcmcia directory. You may need to do some experimentation to find a module that will work with your network card.

You will need to edit /etc/pcmcia/network.opts (for an Ethernet card) or /etc/pcmcia/wireless.opts (if you have a wireless networking card). Like most Slackware configuration files, these two files are very well commented and it should be easy to determine which modifications need to be made.

5.3.1 DHCP

DHCP (or Dynamic Host Configuration Protocol), is a means by which an IP address may be assigned to a computer on boot. When the DHCP client boots, it puts out a request on the Local Area Network for a DHCP server to assign it an IP address. The DHCP server has a pool (or scope) of IP addresses available. The server will respond to this request with an IP address from the pool, along with a lease time. Once the lease time for a given IP address lease has expired, the client must contact the server again and repeat the negotiation.

The client will then accept the IP address from the server and will configure the requested interface with the IP address. There is one more handy trick that DHCP clients use for negotiating the IP address that they will be assigned, however. The client will remember it's last assigned IP address, and will request that the server re-assign that IP address to the client again upon next negotiation. If possible, the server will do so, but if not, a new address is assigned. So, the negotiation resembles the following:

    Client: Is there a DHCP server available on the LAN?
    Server: Yes, there is. Here I am.
    Client: I need an IP address.
    Server: You may take 192.168.10.10 for 19200 seconds.
    Client: Thank you.

    Client: Is there a DHCP server available on the LAN?
    Server:Yes, there is. Here I am.
    Client:I need an IP address. The last time we
    talked, I had 192.168.10.10;
    May I have it again?
    Server:Yes, you may (or No, you may not: take 192.168.10.12 instead).
    Client: Thank you.

The DHCP client in Linux is /sbin/dhcpcd. If you load /etc/rc.d/rc.inet1 in your favorite text editor, you will notice that /sbin/dhcpcd is called about midway through the script. This will force the conversation shown above. dhcpcd will also track the amount of time left on the lease for the current IP address, and will automatically contact the DHCP server with a request to renew the lease when necessary. DHCP can also control related information, such as what ntp server to use, what route to take, etc.

Setting up DHCP on Slackware is simple. Just run netconfig and select DHCP when offered. If you have more than one NIC and do not wish eth0 to be configured by DHCP, just edit the /etc/rc.d/rc.inet1.conf file and change the related variable for your NIC to “YES”.

5.3.2 Static IP

Static IP addresses are fixed addresses that only change if manually told to. These are used in any case where an administrator doesn't want the IP information to change, such for internal servers on a LAN, any server connected to the Internet, and networked routers. With static IP addressing, you assign an address and leave it at that. Other machines know that you are always at that certain IP address and can contact you at that address always.

5.3.3 /etc/rc.d/rc.inet1.conf

If you plan on assigning an IP address to your new Slackware box, you may do so either through the netconfig script, or you may edit /etc/rc.d/rc.inet1.conf. In /etc/rc.d/rc.inet1.conf , you will notice:

    # Primary network interface card (eth0)
    IPADDR[0]=""
    NETMASK[0]=""
    USE_DHCP[0]=""
    DHCP_HOSTNAME[0]=""

Then further at the bottom:

    GATEWAY=""

In this case, our task is merely to place the correct information between the double-quotes. These variables are called by /etc/rc.d/rc.inet1 at boot time to setup the nics. For each NIC, just enter the correct IP information, or put “YES” for USE_DHCP. Slackware will startup the interfaces with the information placed here in the order they are found.

The DEFAULT_GW variable sets up the default route for Slackware. All communications between your computer and other computers on the Internet must pass through that gateway if no other route is specified for them. If you are using DHCP, you will usually not need to enter anything here, as the DHCP server will specify what gateway to use.

5.3.4 /etc/resolv.conf

Ok, so you've got an IP address, you've got a default gateway, you may even have ten million dollars (give us some), but what good is that if you can't resolve names to IP addresses? No one wants to type in 72.9.234.112 into their web browser to reach www.slackbook.org. After all, who other than the authors would memorize that IP address? We need to setup DNS, but how? That's where /etc/resolv.conf comes into play.

Chances are you already have the proper options in /etc/resolv.conf. If you setup your network connection using DHCP, the DHCP server should handle updating this file for you. (Technically the DHCP server just tells dhcpcd what to put here, and it obeys.) If you need to manually update your DNS server list though, you'll need to hand edit /etc/resolv.conf. Below is an example:

# cat /etc/resolv.conf
nameserver 192.168.1.254
search lizella.net

The first line is simple. The nameserver directive tells us what DNS servers to query. By necessity these are always IP addresses. You may have as many listed there as you like. Slackware will happily check one after the other until one returns a match.

The second line is a little more interesting. The search directive gives us a list of domain names to assume whenever a DNS request is made. This allows you to contact a machine by only the first part of its FQDN (Fully Qualified Domain Name). For example, if “slackware.com” were in your search path, you could reach http://store.slackware.com by just pointing your web browser at http://store.

# ping -c 1 store
PING store.slackware.com (69.50.233.153): 56 data bytes
64 bytes from 69.50.233.153 : icmp_seq=0 ttl=64 time=0.251 ms
1 packets transmitted, 1 packets received, 0% packet loss
round-trip min/avg/max = 0.251/0.251/0.251 ms

5.3.5 /etc/hosts

Now that we've got DNS working fine, what if we want to bypass our DNS server, or add a DNS entry for a machine that isn't in DNS? Slackware includes the oft-loved /etc/hosts file which contains a local list of DNS names and IP addresses they should match to.

# cat /etc/hosts
127.0.0.1           localhost  locahost.localdomain
192.168.1.101       redtail
172.14.66.32        foobar.slackware.com

Here you can see that localhost has an IP address of 127.0.0.1 (always reserved for localhost), redtail can be reached at 192.168.1.101, and foobar.slackware.com is 172.14.66.32.

5.4.1 pppsetup

Slackware includes a program called pppsetup to configure your system to use your dialup account. It shares a look and feel similar to our netconfig program. To run the program, make sure you are logged in as root. Then type pppsetup to run it. You should see a screen like this:

The program will present a series of questions, to which you will feed it appropriate answers. Things like your modem device, the modem initialization string, and the ISP phone number. Some items will have a default, which you can accept in most cases.

After the program runs, it will create a ppp-go program and a ppp-off program. These are used to start and stop, respectively, the PPP connection. The two programs are located in /usr/sbin and need root privileges to run.

5.4.2 /etc/ppp

For most users, running pppsetup will be sufficient. However, there may be an instance where you want to tweak some of the values used by the PPP daemon. All of the configuration information is kept in /etc/ppp. Here is a list of what the different files are for:

Most of these files won't be there until after you run pppsetup.

5.5.1 Hardware Support

Hardware support for a wireless card is provided through the kernel, either with a module or built in to the kernel. Generally, most newer Ethernet cards are provided through kernel modules, so you'll want to determine the appropriate kernel module and load it through /etc/rc.d/rc.modules. netconfig may not detect your wireless card, so you'll probably need to determine the card yourself. See http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/ for more information on kernel drivers for various wireless cards.

5.5.2 Configure the Wireless Settings

The vast majority of this work is done by iwconfig, so as always read the man page for iwconfig if you need more information.

First, you'll want to configure your wireless access point. Wireless access points vary quite a bit in their terminology, and how to configure them, so you may need to adjust a bit to accommodate your hardware. In general, you'll need at least the following information:

• The domain ID, or name of the network (called the ESSID by iwconfig)

• The channel the WAP uses

• The encryption settings, including any keys used (preferably in hexadecimal)

A NOTE ABOUT WEP. WEP is quit flawed, but it's much better than nothing. If you wish a greater degree of security on your wireless network, you should investigate VPNs or IPSec, both of which are beyond the scope of this document. You might also configure your WAP not to advertise its domain ID/ ESSID. A thorough discussion of wireless policy is beyond the scope of this section, but a quick Google search will turn up more than you ever wanted to know.

Once you've gathered the above information, and assuming you've used modprobe to load the appropriate kernel driver, you can edit rc.wireless.conf and add your settings. The rc.wireless.conf file is a bit untidy. The least effort is to modify the generic section with your ESSID and KEY, and CHANNEL if required by your card. (Try not setting CHANNEL, and if it works, great; if not, set the CHANNEL as appropriate.) If you're daring, you can modify the file so that only the necessary variables are set. The variable names in rc.wireless.conf correspond to the iwconfig parameters, and are read by rc.wireless and used in the appropriate iwconfig commands.

If you have your key in hexadecimal, that's ideal, since you can be fairly confident that your WAP and iwconfig will agree on the key. If you only have a string, you can't be sure how your WAP will translate that into a hexadecimal key, so some guesswork may be needed (or get your WAP's key in hex).

Once you've modified rc.wireless.conf, run rc.wireless as root, then run rc.inet1, again as root. You can test your wireless networking with standard testing tools such as ping, along with iwconfig. If you have a wired interface you may wish to use ifconfig to turn those interfaces off while you test your wireless networking to ensure there's no interference. You may also want to test your changes through a reboot.

Now that you've seen how to edit /etc/rc.d/rc.wireless for you default network, let's take a closer look at iwconfig and see how it all works. This will teach you the quick and dirty way of setting up wifi for those times when you find yourself at an Internet cafe, coffee shop, or any other wifi hot spot and wish to get online.

The first step is to tell your wireless NIC what network to join. Make sure you replace “eth0” with whatever network interface your wireless card uses and change “mynetwork” to the essid you wish to use. Yes, we know you're smarter than that. Next you'll have to specify the encryption key (if any) used on your wireless network. Finally specify the channel to use (if needed).

# iwconfig eth0 essid "mynetwork"
# iwconfig eth0 key XXXXXXXXXXXXXXXXXXXXXXXXXXX
# iwconfig eth0 channel n

That should be all on the wireless end of things.

5.5.3 Configure the Network

This is done in the exact same way as wired networks. Simply refer to earlier sections of this chapter.

5.6.1 SMB/Samba/CIFS

SMB (for Server Message Block) is a descendant of the older NetBIOS protocol that was initially used by IBM in their LAN Manager product. Microsoft has always been fairly interested in NetBIOS and it's successors (NetBEUI, SMB and CIFS). The Samba project has existed since 1991, when it was originally written to link an IBM PC running NetBIOS with a Unix server. These days, SMB is the preferred method for sharing file and print services over a network for virtually the entire civilized world because Windows supports it.

Samba's configuration file is /etc/samba/smb.conf; one of the most well commented and documented configuration files you will find anywhere. Sample shares have been setup for you to view and modify for your needs. If you need even tighter control the man page for smb.conf is indispensable. Since Samba is documented so well in the places I've mentioned above, we will not rewrite the documentation here. We will, however, quickly cover the basics.

smb.conf is broken down into multiple sections: one section per share, and a global section for setting options that are to be used everywhere. Some options are only valid in the global section; some are only valid outside the global section. Remember that the global section can be over-ridden by any other section. Refer to the man pages for more information.

You will most likely wish to edit your smb.conf file to reflect the network settings in your LAN. I would suggest modifying the items listed below:

[global]
# workgroup = NT-Domain-Name or Workgroup-Name, eg: LINUX2
workgroup = MYGROUP

Change the workgroup name to reflect the workgroup or domain name that you are using locally.

# server string is the equivalent of the NT Description field
server string = Samba Server

This will be the name of your Slackware computer displayed in the Network Neighborhood (or My Network Places) folder.

# Security mode. Most people will want user level security. See
# security_level.txt for details. NOTE: To get the behaviour of
# Samba-1.9.18, you'll need to use "security = share".
security = user

You'll almost certainly wish to implement user level security on your Slackware system.

# You may wish to use password encryption. Please read
# ENCRYPTION.txt, Win95.txt and WinNT.txt in the Samba
# documentation.
# Do not enable this option unless you have read those documents
encrypt passwords = yes

If encrypt passwords is not enabled, you will not be able to use Samba with NT4.0, Win2k, WinXP, and Win2003. Earlier Windows operating systems did not require encryption to share files.

SMB is an authenticated protocol, meaning you must supply a correct username and password in order to use this service. We tell the samba server what usernames and passwords are valid with the smbpasswd command. smbpasswd takes a couple of common switches to tell it to either add traditional users, or add machine users (SMB requires that you add the computers' NETBIOS names as machine users, restricting what computers one can authenticate from).

Adding a user to the /etc/samba/private/smbpasswd file.
# smbpasswd -a user
Adding a machine name to the /etc/samba/private/smbpasswd file.
# smbpasswd -a -m machine

It's important to note that a given username or machine name must already exist in the /etc/passwd file. You can accomplish this simply with the adduser command. Note that when using the adduser command to add a machine name one must append a dollar sign (“$”) to the machine name. This should not however, be done with smbpasswd. smbpasswd appends the dollar sign on its own. Failing to mangle the machine name this way with adduser will result in an error when adding the machine name to samba.

# adduser machine$

5.6.2 Network File System (NFS)

NFS (or Network File System) was originally written by Sun for their Solaris implementation of Unix. While it is significantly easier to get up and running when compared to SMB, it is also significantly less secure. The primary insecurity in NFS is that it is easy to spoof user and group id's from one machine to another. NFS is an unauthenticated protocol. Future versions of the NFS protocol are being devised that enhance security, but these are not common at the time of this writing.

NFS configuration is governed by the /etc/exports file. When you load the default /etc/exports file into an editor, you'll see a blank file with a two line comment on top. We'll need to add a line to the exports file for each directory that we wish to export, with a listing of client workstations that will be allowed to access that file. For instance, if we wished to export directory /home/foo to workstation Bar, we would simply add the line:

/home/foo Bar(rw)

to our /etc/exports. Below, you'll find the example from the man page for the exports file:

# sample /etc/exports file
/               master(rw) trusty(rw,no_root_squash)
/projects       proj*.local.domain(rw)
/usr            *.local.domain(ro) @trusted(rw)
/home/joe       pc001(rw,all_squash,anonuid=150,anongid=100)
/pub            (ro,insecure,all_squash)

As you can see, there are various options available, but most should be fairly clear from this example.

NFS works under the assumption that a given user on one machine in a network has the same user ID on all machines across the network. When an attempt is made to read or write from a NFS client to an NFS server, a UID is passed as part of the read/write request. This UID is treated the same as if the read/write request originated on the local machine. As you can see, if one could arbitrarily specify a given UID when accessing resources on a remote system, Bad Things (tm) could and would happen. As a partial hedge against this, each directory is mounted with the root_squash option. This maps the UID for any user claiming to be root to a different UID, thus preventing root access to the files or folders in the exported directory. root_squash seems to be enabled by default as a security measure, but the authors recommend specifying it anyway in your /etc/exports file.

You can also export a directory directly from the command line on the server by using the exportfs command as follows:

# exportfs -o rw,no_root_squash Bar:/home/foo

This line exports the /home/foo directory to the computer “Bar” and grants Bar read/write access. Additionally, the NFS server will not invoke root_squash, which means any user on Bar with a UID of “0” (root's UID) will have the same privileges as root on the server. The syntax does look strange (usually when a directory is specified in computer:/directory/file syntax, you are referring to a file in a directory on a given computer).

You'll find more information on the man page for the exports file.

7.3.1 Windows

Setting up a computer with both MS Windows and Linux is probably the most common dual boot scenario. There are numerous ways you can setup the booting, but this section will cover two.

Often times when setting up a dual boot system, a person will devise a perfect plan for where everything should go but mess up the installation order. It is very important to understand that operating systems need to be installed in a certain order for a dual boot setup to work. Linux always offers control over what, if anything, gets written to the Master Boot Record. Therefore, it's always advisable to install Linux last. Windows should be installed first, since it will always write its booter to the Master Boot Record, overwriting any entry Linux may have put there.

   20GB   Windows boot (C:)
   1GB   Linux root (/)
   19GB  Linux /usr (/usr)

# mkdir /win
# mount -t vfat /dev/hda1 /win
# mkdir /win/linux
# cd /root
# cp loadlin* /win/linux
# cp /boot/vmlinuz /win/linux
# cd /win/linuz
# unzip loadlin16a.zip

C:\> cd \
C:\> attrib -r -a -s -h MSDOS.SYS
C:\> edit MSDOS.SYS

BootGUI=0

cls
echo System Boot Menu
echo.
echo 1 - Linux
echo 2 - Windows
echo.
choice /c:12 "Selection? -> "
if errorlevel 2 goto WIN
if errorlevel 1 goto LINUX
:LINUX
cls
echo "Starting Linux..."
cd \linux
loadlin c:\linux\vmlinuz root=/dev/hda2 ro
goto END
:WIN
cls
echo "Starting Windows..."
win
goto END
:END

# dd if=/dev/hda2 of=/tmp/bootsect.lnx bs=1 count=512

C:\WINNT> cd \
C:\> attrib -r -a -s -h boot.ini
C:\> edit boot.ini

C:\bootsect.lnx="Slackware Linux"

7.3.2 Linux

Yes, people really do this. This is definitely the easiest dual boot scenario. You can simply use LILO and add more entries to the /etc/lilo.conf file. That's all there is to it.

8.1.1 Logging In

So you've booted, and you're looking at something that looks like this:

Welcome to Linux 2.4.18
Last login: Wed Jan   1 15:59:14 -0500 2005 on tty6.
darkstar login:

Hmm.. nobody said anything about a login. And what's a darkstar? Don't worry; you probably didn't accidentally fire up a hyperspace comm-link to the Empire's artificial moon. (I'm afraid the hyperspace comm-link protocol isn't currently supported by the Linux kernel. Maybe the 2.8 kernel branch will at last provide this oft looked-for support.) No, darkstar is just the name of one of our computers, and its name gets stamped on as the default. If you specified a name for your computer during setup, you should see it instead of darkstar.

As for the login... If this is your first time, you'll want to log in as root. You'll be prompted for a password; if you set one during the setup process, that's what it's looking for. If not, just hit enter. That's it-- you're in!

8.1.2 Root: The Superuser

Okay, who or what is root? And what's it doing with an account on your system?

Well, in the world of Unix and similar operating systems (like Linux), there are users and then there are users. We'll go into this in more detail later, but the important thing to know now is that root is the user above all users; root is all-powerful and all-knowing, and nobody disobeys root. It just isn't allowed. root is what we call a “superuser”, and rightly so. And best of all, root is you.

Cool, huh?

If you're not sure: yes, that's very cool. The catch is, though, that root is inherently allowed to break anything it so desires. You might want to skip ahead to Section 12.1.1 and see about adding a user; then login as that user and work from there. The traditional wisdom is that it's best to only become the superuser when absolutely necessary, so as to minimize the possibility of accidentally breaking something.

By the way, if you decide you want to be root while you're logged in as someone else, no problem. Just use the su(1) command. You'll be asked for root's password and then it will make you root until you exit or logout. You can also become any other user using su, provided you know that user's password: su logan, for instance, would make you me.

root is allowed to su to any user, without requiring their password.

8.2.1 Running Programs

It's hard to get much accomplished without running a program; you might be able to prop something up with your computer or hold a door open, and some will make the most lovely humming noise when running, but that's really about it. And I think we can all agree that its use as a humming doorstop isn't what brought the personal computer the popularity it now enjoys.

So, remember how almost everything in Linux is a file? Well, that goes for programs, too. Every command you run (that isn't built into the shell) resides as a file somewhere. You run a program simply by specifying the full path to it.

For instance, remember that su command from the last section? Well, it's actually in the /bin directory: /bin/su would run it nicely.

So why, then, does just typing su work? After all, you didn't say it was in /bin. It could just as easily have been in /usr/local/share, right? How did it know? The answer to that lies in the PATH environment variable; most shells have either PATH or something very much like PATH. It basically contains a list of directories to look in for programs you try to run. So when you ran su, your shell ran through its list of directories, checking each one for an executable file called su that it could run; the first one it came to, it ran. This happens whenever you run a program without specifying a full path to it; if you get a ““Command not found”” error, that only means that the program you tried to run isn't in your PATH. (Of course, this would be true if the program doesn't exist at all...) We'll discuss environment variables in more depth in Section 8.3.1.

Remember also that “.” is shorthand for the current directory, so if you happened to be in /bin, ./su would have worked as an explicit full path.

8.2.2 Wildcard Matching

Nearly every shell recognizes some characters as being substitutes or abbreviations that mean anything goes here. Such characters are aptly named wildcards; the most common are * and ?. By convention, ? usually matches any single character. For instance, suppose you're in a directory with three files: ex1.txt, ex2.txt, and ex3.txt. You want to copy all of those files (using the cp command we cover in Section 10.5.1) to another directory, say /tmp. Well, typing cp ex1.txt ex2.txt ex3.txt /tmp is entirely too much work. It's much easier to type cp ex?.txt /tmp; the ? will match each of the characters “1”, “2”, and “3”, and each in turn will be substituted in.

What's that you say? That's still too much work? You're right. It's appalling; we have labor laws to protect us from that sort of thing. Fortunately, we also have *. As was already mentioned, * matches “any number of characters”, including 0. So if those three files were the only ones in the directory, we could have simply said cp * /tmp and gotten them all in one fell swoop. Suppose, though, that there is also a file called ex.txt and one called hejaz.txt. We want to copy ex.txt but not hejaz.txt; cp ex* /tmp will do that for us.

cp ex?.txt /tmp, would, of course, only get our original three files; there's no character in ex.txt to match that ?, so it would be left out.

Another common wildcard is the bracket pair [ ]. Any characters inside the brackets will be substituted in place of the [ ] to find matches. Sound confusing? It's not too bad. Suppose for instance, we have a directory containing the following 8 files: a1, a2, a3, a4, aA, aB, aC, and aD . We want to only find the files ending in numbers; [ ] will do this for us.

% ls a[1-4]
a1 a2 a3 a4

But what we really want is just a1, a2, and a4? In the previous example we used - to mean all values between 1 and 4. We can also separate individual entries with commas.

% ls a[1,2,4]
a1 a2 a4

I know what you're thinking now, “Well what about letters?” Linux is case-sensitive, meaning that a and A are different characters and are only related in your mind. Capitals always come before lowercase letters, so A and B come before a and b. Continuing with our earlier example, if we wanted files a1, and A1, we can find these quickly with [ ].

% ls [A,a]1
A1 a1

Note, that if we had included a hyphen instead of a comma, we would have gotten incorrect results.

% ls [A-a]1
A1 B1 C1 D1 a1

You can also combine hyphen and comma strings.

% ls [A,a-d]
A1 a1 b1 c1 d1

8.2.3 Input/Output Redirection and Piping

(Here comes something cool.)

% ps > blargh

Y'know what that is? That's me running ps to see which processes are running; ps is covered in Section 11.3. That's not the cool part. The cool part is > blargh, which means, roughly, take the output from ps and write it to a file called blargh. But wait, it gets cooler.

% ps | less

That one takes the output from ps and pipes it through less, so I can scroll through it at my leisure.

% ps >> blargh

This is the third most commonly used redirector; it does the same thing as “>”, except that “>>” will append output from ps to the file blargh, if said file exists. If not, just like “>”, it will be created. (“>” will obliterate the current contents of blargh.)

There is also a “<” operator, which means take your input from the following, but it's not used nearly so often.

% fromdos < dosfile.txt > unixfile.txt

Redirection gets really fun when you start piling it up:

% ps | tac >> blargh

That will run ps, reverse the lines of its output, and append those to the file blargh. You can stack as many of these up as you want; just be careful to remember that they get interpreted from left to right.

See the bash(1) man page for more detailed information on redirection.

8.3.1 Environment Variables

A Linux system is a complex beast, and there's a lot to keep track of, a lot of little details that come into play in your normal interactions with various programs (some of which you might not even need to be aware of). Nobody wants to pass a bunch of options to every program that gets run, telling it what kind of terminal is being used, the hostname of the computer, how their prompt should look...

So as a coping mechanism, users have what's called an environment. The environment defines the conditions in which programs run, and some of this definition is variable; the user can alter and play with it, as is only right in a Linux system. Pretty much any shell will have environment variables (if not, it's probably not a very useable shell). Here we will give an overview of the commands bash provides for manipulating its environment variables.

set by itself will show you all of the environment variables that are currently defined, as well as their values. Like most bash built-ins, it can also do several other things (with parameters); we'll leave it to the bash(1) man page to cover that, though. Example 8-1 shows an excerpt from a set command run on one of the author's computers. Notice in this example the PATH variable that was discussed earlier. Programs in any of those directories can be run simply by typing the base filename.

% set
PATH=/usr/local/lib/qt/bin:/usr/local/bin:/usr/bin:/bin:/usr/X11R6/bin:
/usr/openwin/bin:/usr/games:.:/usr/local/ssh2/bin:/usr/local/ssh1/bin:
/usr/share/texmf/bin:/usr/local/sbin:/usr/sbin:/home/logan/bin
PIPESTATUS=([0]="0")
PPID=4978
PS1='\h:\w\$ '
PS2='> '
PS4='+ '
PWD=/home/logan
QTDIR=/usr/local/lib/qt
REMOTEHOST=ninja.tdn
SHELL=/bin/bash

% unset VARIABLE

unset will remove any variables that you give it, wiping out both the variable and its value; bash will forget that variable ever existed. (Don't worry. Unless it's something you explicitly defined in that shell session, it'll probably get redefined in any other session.)

% export VARIABLE=some_value

Now, export is truly handy. Using it, you give the environment variable VARIABLE the value “some_value”; if VARIABLE didn't exist, it does now. If VARIABLE already had a value, well, it's gone. That's not so good, if you're just trying to add a directory to your PATH. In that case, you probably want to do something like this:

% export PATH=$PATH:/some/new/directory

Note the use of $PATH there: when you want bash to interpret a variable (replace it with its value), tack a $ onto the beginning of the variable's name. For instance, echo $PATH will echo the value of PATH, in my case:

% echo $PATH
/usr/local/lib/qt/bin:/usr/local/bin:/usr/bin:/bin:/usr/X11R6/bin:
/usr/openwin/bin:/usr/games:.:/usr/local/ssh2/bin:/usr/local/ssh1/bin:
/usr/share/texmf/bin:/usr/local/sbin:/usr/sbin:/home/logan/bin

8.3.2 Tab Completion

(Here comes something cool again.)

1. A commandline interface means lots of typing.

2. Typing is work.

3. Nobody likes work.

From 3 and 2, we can determine that (4) nobody likes typing. Fortunately, bash saves us from (5) (nobody likes a commandline interface).

How does bash accomplish this wonderful feat, you ask? In addition to the wildcard expansion we discussed before, bash features tab completion.

Tab completion works something like this: You're typing the name of a file. Maybe it's in your PATH, maybe you're typing it out explicitly. All you have to do is type enough of the filename to uniquely identify it. Then hit the tab key. bash will figure out what you want and finish typing it for you!

Example time. /usr/src contains two subdirectories: /usr/src/linux and /usr/src/sendmail. I want to see what's in /usr/src/linux. So I just type ls /usr/src/l, hit the TAB key, and bash gives me ls /usr/src/linux.

Now, suppose there are two directories /usr/src/linux and /usr/src/linux-old; If I type /usr/src/l and hit TAB, bash will fill in as much as it can, and I'll get /usr/src/linux. I can stop there, or I can hit TAB again, and bash will show a list of directories that match what I've typed so far.

Hence, less typing (and hence, people can like commandline interfaces). I told you it was cool.

8.4.1 Screen

But what about situations where there are no virtual terminals? What then? Fortunately, slackware includes a beautiful screen manager aptly named screen. screen is a terminal emulator that has virtual terminal like capabilities. Executing screen flashes a brief introduction, then dumps to a terminal. Unlike the standard virtual terminals, screen has its own commands. All screen commands are prefixed with a Crtl+A keystroke. For example, Ctrl+A+C will create a new terminal session. Ctrl+A+N will switch to the next terminal. Ctrl+A+P switches to the previous terminal.

screen also supports detaching and re-attaching to screen sessions which is particularly useful for remote sessions via ssh and telnet, (more on those later). Ctrl+A+D will detach from the currently running screen. Executing screen -r will list all currently running screen sessions you may reattach to.

% screen -r
There are several suitable screens on:
     1212.pts-1.redtail      (Detached)
     1195.pts-1.redtail      (Detached)
     1225.pts-1.redtail      (Detached)
     17146.pts-1.sanctuary   (Dead ???)
Remove dead screens with 'screen -wipe'.
Type "screen [-d] -r [pid.]tty.host" to resume one of them. 

Running screen -r 1212 would reattach to the first screen listed. I mentioned earlier how useful this was for remote sessions. If I were to login to a remote slackware server via ssh, and my connection was severed by some chance occurrence such as a local power failure, whatever I was doing at that moment would instantly perish, which can be a horrible thing for your server. Using screen prevents this by detaching my session if my connection is dropped. Once my connection is restored, I can reattach to my screen session and resume right where I left off.

9.4.1 fstab

Let's look at an example of the /etc/fstab file:

% cat /etc/fstab
/dev/sda1       /               ext2        defaults        1   1
/dev/sda2       /usr/local      ext2        defaults        1   1
/dev/sda4       /home           ext2        defaults        1   1
/dev/sdb1       swap            swap        defaults        0   0
/dev/sdb3       /export         ext2        defaults        1   1
none            /dev/pts        devpts      gid=5,mode=620  0   0
none            /proc           proc        defaults        0   0
/dev/fd0        /mnt            ext2        defaults        0   0
/dev/cdrom      /mnt/cdrom      iso9660     ro              0   0

The first column is the device name. In this case, the devices are five partitions spread out across two SCSI hard drives, two special filesystems that don't need a device, a floppy, and a CD-ROM drive. The second column is where the device will be mounted. This needs to be a directory name, except in the case of a swap partition. The third column is the filesystem type of the device. For normal Linux filesystems, this will be ext2 (second extended filesystem). CD-ROM drives are iso9660, and Windows-based devices will either be msdos or vfat.

The fourth column is a listing of options that apply to the mounted filesystem. defaults is fine for just about everything. However, read-only devices should be given the ro flag. There are a lot of options that can be used. Check the fstab(5) man page for more information. The last two columns are used by fsck and other commands that need to manipulate the devices. Check the man page for that information as well.

When you install Slackware Linux, the setup program will build much of the fstab file.

9.4.2 mount and umount

Attaching another device to your filesystem is easy. All you have to do is use the mount command, along with a few options. Using mount can simplified if the device has an entry in the /etc/fstab file. For example, let's say that I wanted to mount my CD-ROM drive and that my fstab file looked like the example from the previous section. I would call mount like so:

% mount /cdrom

Since there is an entry in fstab for that mount point, mount knows what options to use. If there wasn't an entry for that device, I would have to use several options for mount:

% mount -t iso9660 -o ro /dev/cdrom /cdrom

That command line includes the same information as the example fstab did, but we'll go over all the parts anyways. The -t iso9660 is the filesystem type of the device to mount. In this case, it would be the iso9660 filesystem which is what CD-ROM drives most commonly use. The -o ro tells mount to mount the device read-only. The /dev/cdrom is the name of the device to mount, and /cdrom is the location on the filesystem to mount the drive.

Before you can remove a floppy, CD-ROM, or other removable device that is currently mounted, you'll have to unmount it. That is done using the umount command. Don't ask where the “n” went because we couldn't tell you. You can use either the mounted device or the mount point as the argument to umount. For example, if you wanted to unmount the CD-ROM from the previous example, either of these commands would work:

# umount /dev/cdrom
# umount /cdrom

10.1.1 ls

This command lists files in a directory. Windows and DOS users will notice its similarity to the dir command. By itself, ls(1) will list the files in the current directory. To see what's in your root directory, you could issue these commands:

% cd /
% ls
bin   cdr    dev  home  lost+found  proc  sbin   tmp  var
boot  cdrom  etc  lib   mnt         root  suncd  usr  vmlinuz

The problem a lot of people have with that output is that you cannot easily tell what is a directory and what is a file. Some users prefer that ls add a type identifier to each listing, like this:

% ls -FC
bin/   cdr/    dev/  home/  lost+found/  proc/  sbin/   tmp/  var/
boot/  cdrom/  etc/  lib/   mnt/         root/  suncd/  usr/  vmlinuz

Directories get a slash at the end of the name, executable files get an asterisk at the end of the name, and so on.

ls can also be used to get other statistics on files. For example, to see the creation dates, owners, and permissions, you would look at a long listing:

% ls -l
drwxr-xr-x   2 root     bin          4096 May  7 09:11 bin/
drwxr-xr-x   2 root     root         4096 Feb 24 03:55 boot/
drwxr-xr-x   2 root     root         4096 Feb 18 01:10 cdr/
drwxr-xr-x  14 root     root         6144 Oct 23 18:37 cdrom/
drwxr-xr-x   4 root     root        28672 Mar  5 18:01 dev/
drwxr-xr-x  10 root     root         4096 Mar  8 03:32 etc/
drwxr-xr-x   8 root     root         4096 Mar  8 03:31 home/
drwxr-xr-x   3 root     root         4096 Jan 23 21:29 lib/
drwxr-xr-x   2 root     root        16384 Nov  1 08:53 lost+found/
drwxr-xr-x   2 root     root         4096 Oct  6 12:47 mnt/
dr-xr-xr-x  62 root     root            0 Mar  4 15:32 proc/
drwxr-x--x  12 root     root         4096 Feb 26 02:06 root/
drwxr-xr-x   2 root     bin          4096 Feb 17 02:02 sbin/
drwxr-xr-x   5 root     root         2048 Oct 25 10:51 suncd/
drwxrwxrwt   4 root     root       487424 Mar  7 20:42 tmp/
drwxr-xr-x  21 root     root         4096 Aug 24 03:04 usr/
drwxr-xr-x  18 root     root         4096 Mar  8 03:32 var/

Suppose you want to get a listing of the hidden files in the current directory. This command will do just that:

% ls -a
.              bin   cdrom  home        mnt   sbin   usr
..             boot  dev    lib         proc  suncd  var
.pwrchute_tmp  cdr   etc    lost+found  root  tmp    vmlinuz

Files beginning with a period (called dot files) are hidden when you run ls. You will only see them if you pass the -a option.

There are many more options that can be found in the online manual page. Don't forget that you can combine options that you pass to ls.

10.1.2 cd

The cd command is used to change working directories. You simply type cd followed by the path name to change to. Here are some examples:

darkstar:~$ cd /bin
darkstar:/bin$ cd usr
bash: cd: usr: No such file or directory
darkstar:/bin$ cd /usr
darkstar:/usr$ ls
bin
darkstar:/usr$ cd bin
darkstar:/usr/bin$

Notice that without the preceding slash, it tries to change to a directory in the current directory. Also executing cd with no options will move you to your home directory.

The cd command is not like the other commands. It is a builtin shell command. Shell builtins are discussed in Section 8.3.1. This may not make any sense to you right now. Basically it means there is no man page for this command. Instead, you have to use the shell help. Like this:

% help cd

It will display the options for cd and how to use them.

10.1.3 pwd

The pwd command is used to show your current location. To use the pwd command just type pwd. For example:

% cd /bin
% pwd
/bin
% cd /usr
% cd bin
% pwd
/usr/bin

10.2.1 more

more(1) is what we call a pager utility. Oftentimes the output of a particular command is too big to fit on one screen. The individual commands do not know how to fit their output to separate screens. They leave this job to the pager utility.

The more command breaks the output into individual screens and waits for you to press the space bar before continuing on to the next screen. Pressing the enter key will advance the output one line. Here is a good example:

% cd /usr/bin
% ls -l

That should scroll for a while. To break up the output screen by screen, just pipe it through more:

% ls -l | more

That is the pipe character (shift backslash). The pipe is short for saying take the output of ls and feed it into more. You can pipe just about anything through the more command, not just ls. Piping is also covered in Section 8.2.3.

10.2.2 less

The more command is quite handy, but often you will find that you have advanced past the screen you wanted. more does not provide a way to go back. The less(1) command provides this functionality. It is used in the same way as the more command, so the previous examples apply here too. So, less is more than more. Joost Kremers puts it this way:

less is more, but more more than more is, so more is less less, so use more less if you want less more.

10.2.3 most

Where more and less leave off, most(1) picks back up. If less is more than more, most is more than less. Whereas the other pagers can only display one file at a time, most is capable of viewing any number of files, as long as each file's window is at least 2 lines long. most has a lot of options, check the man page for full details.

10.3.1 cat

cat(1) is short for “concatenate”. It was originally designed to merge text files into one, but can be used for many other purposes.

To merge two or more files into one, you simply list the files after the cat command and then redirect the new output to a file. cat works with standard input and standard output, so you have to use the shell redirection characters. For example:

% cat file1 file2 file3 > bigfile

This command takes the contents of file1, file2, and file3 and merges it all together. The new output is sent to standard out.

One can also use cat to display files. Many people cat text files through the more or less commands, like this:

% cat file1 | more

That will display the file1 file and pipe it through the more command so that you only get one screen at a time.

Another common use for cat is copying files. You can copy any file around with cat, like this:

% cat /bin/bash > ~/mybash

The /bin/bash program is copied to your home directory and named mybash.

cat has many uses and the ones discussed here are just a few. Since cat makes extensive use of standard input and standard output, it is ideal for use in shell scripts or part of other complex commands.

10.3.2 echo

The echo(1) command displays the specified text on the screen. You specify the string to display after the echo command. By default echo will display the string and print a newline character after it. You can pass the -n option to suppress the printing of the newline. The -e option will cause echo to search for escape characters in the string and execute them.

10.4.1 touch

touch(1) is used to change the timestamp on a file. You can change access timestamps and modification timestamps with this command. If the file specified does not exist, touch will create a zero length file with the name specified. To mark a file with the current system time, you would issue this command:

% ls -al file1
-rw-r--r--    1 root     root        9779 Feb  7 21:41 file1
% touch file1
% ls -al file1
-rw-r--r--    1 root     root        9779 Feb  8 09:17 file1

There are several options for touch, including options to specify which timestamp to modify, the time to use, and many more. The online manual page discusses these in detail.

10.4.2 mkdir

mkdir(1) will create a new directory. You simply specify the directory to create when you run mkdir. This example creates the hejaz directory in the current directory:

% mkdir hejaz

You can also specify a path, like this:

% mkdir /usr/local/hejaz

The -p option will tell mkdir to make any parent directories. The above example will fail if /usr/local does not exist. The -p option will create /usr/local and /usr/local/hejaz:

% mkdir -p /usr/local/hejaz

10.5.1 cp

cp(1) copies files. DOS users will notice its similarity to the copy command. There are many options for cp , so you should have a look at the man page before using it.

A common use is to use cp to copy a file from one location to another. For example:

% cp hejaz /tmp

This copies the hejaz file from the current directory to the /tmp directory.

Many users prefer to keep the timestamps preserved, as in this example:

% cp -a hejaz /tmp

This ensures that the timestamps are not modified in the copy.

To recursively copy the contents of a directory to another directory, you would issue this command:

% cp -R mydir /tmp

That will copy the mydir directory to the /tmp directory.

Also if you wish to copy a directory or a file and keep all it's old permissions and time stamps and keep it exactly the same use cp -p.

% ls -l file
-rw-r--r--    1 root     vlad            4 Jan  1 15:27 file
% cp -p file /tmp
% ls -l /tmp/file
-rw-r--r--    1 root     vlad            4 Jan  1 15:27 file

cp has many more options that are discussed in detail in the online manual page.

10.5.2 mv

mv(1) moves files from one place to another. Sounds simple enough doesn't it?

% mv oldfile /tmp/newfile

mv has a few useful command line options that are detailed in the man page. In practice, mv is almost never used with commandline options.

10.6.1 rm

rm(1) removes files and directory trees. DOS users will notice the similarity to both the del and deltree commands. rm can be very dangerous if you do not watch yourself. While it is sometimes possible to retrieve a recently deleted file, it can be complicated (and potentially costly) and is beyond the scope of this book.

To remove a single file, specify its name when you run rm:

% rm file1

If the file has write permissions removed, you may get a permission denied error message. To force removal of the file no matter what, pass the -f option, like this:

% rm -f file1

To remove an entire directory, you use the -r and -f options together. This is a good example of how to delete the entire contents of your hard drive. You really don't want to do this. But here's the command anyway:

# rm -rf /

Be very careful with rm; you can shoot yourself in the foot. There are several command line options, which are discussed in detail in the online manual page.

10.6.2 rmdir

rmdir(1) removes directories from the filesystem. The directory must be empty before it can be removed. The syntax is simply:

% rmdir <directory>

This example will remove the hejaz subdirectory in the current working directory:

% rmdir hejaz

If that directory does not exist, rmdir will tell you. You can also specify a full path to a directory to remove, as this example shows:

% rmdir /tmp/hejaz

That example will try to remove the hejaz directory inside the /tmp directory.

You can also remove a directory and all of its parent directories by passing the -p option.

% rmdir -p /tmp/hejaz

This will first try to remove the hejaz directory inside /tmp. If that is successful, it will try to remove /tmp. rmdir will continue this until an error is encountered or the entire tree specified is removed.

12.1.1 Supplied Scripts

The easiest way to manage users and groups is with the supplied scripts and programs. Slackware includes the programs adduser, userdel(8), chfn(1), chsh(1), and passwd(1) for dealing with users. The commands groupadd(8), groupdel(8), and groupmod(8) are for dealing with groups. With the exception of chfn, chsh, and passwd, these programs are generally only run as root, and are therefore located in /usr/sbin. chfn, chsh, and passwd can be run by anyone, and are located in /usr/bin.

Users can be added with the adduser program. We'll start out by going through the whole procedure, showing all the questions that are asked and a brief description of what everything means. The default answer is in the brackets, and can be chosen for almost all the questions, unless you really want to change something.

# adduser
Login name for new user []: jellyd

This is the name that the user will use to login. Traditionally, login names are eight characters or fewer, and all lowercase characters. (You may use more than eight characters, or use digits, but avoid doing so unless you have a fairly important reason.)

You can also provide the login name as an argument on the command line:

# adduser jellyd

In either case, after providing the login name, adduser will prompt for the user ID:

User ID ('UID') [ defaults to next available ]:

The user ID (UID) is how ownerships are really determined in Linux. Each user has a unique number, starting at 1000 in Slackware. You can pick a UID for the new user, or you can just let adduser assign the user the next free one.

Initial group [users]:

All users are placed into the users group by default. You might want to place the new user into a different group, but it is not recommended unless you know what you're doing.

Additional groups (comma separated) []:

This question allows you to place the new user into additional groups. It is possible for a user to be in several groups at the same time. This is useful if you have established groups for things like modifying web site files, playing games, and so on. For example, some sites define group wheel as the only group that can use the su command. Or, a default Slackware installation uses the sys group for users authorized to play sounds through the internal sound card.

Home directory [/home/jellyd]

Home directories default to being placed under /home. If you run a very large system, it's possible that you have moved the home directories to a different location (or to many locations). This step allows you to specify where the user's home directory will be.

Shell [ /bin/bash ]

bash is the default shell for Slackware Linux, and will be fine for most people. If your new user comes from a Unix background, they may be familiar with a different shell. You can change their shell now, or they can change it themselves later using the chsh command.

Expiry date (YYYY-MM-DD) []:

Accounts can be set up to expire on a specified date. By default, there is no expiration date. You can change that, if you'd like. This option might be useful for people running an ISP who might want to make an account expire upon a certain date, unless they receive the next year's payment.

New account will be created as follows:
---------------------------------------
Login name:         jellyd
UID:                [ Next available ]
Initial group:      users
Additional groups:  [ None ]
Home directory:     /home/jellyd
Shell:              /bin/bash
Expiry date:        [ Never ]

This is it... if you want to bail out, hit Control+C. Otherwise, press ENTER to go ahead and make the account.

You now see all the information that you've entered about the new account and are given the opportunity to abort the account creation. If you entered something incorrectly, you should hit Control+C and start over. Otherwise, you can hit enter and the account will be made.

Creating new account...

Changing the user information for jellyd
Enter the new value, or press return for the default
        Full Name []: Jeremy
        Room Number []: Smith 130
        Work Phone []:
        Home Phone []:
        Other []:

All of this information is optional. You don't have to enter any of this if you don't want to, and the user can change it at any time using chfn. However, you might find it helpful to enter at least the full name and a phone number, in case you need to get in touch with the person later.

Changing password for jellyd
Enter the new password (minimum of 5, maximum of 127 characters)
Please use a combination of upper and lower case letters and numbers.
New password:
Re-enter new password:
Password changed.

Account setup complete.

You'll have to enter a password for the new user. Generally, if the new user is not physically present at this point, you'll just pick some default password and tell the user to change it to something more secure.

Choosing a Password: Having a secure password is the first line of defense against getting cracked. You do not want to have an easily guessed password, because that makes it easier for someone to break into your system. Ideally, a secure password would be a random string of characters, including upper and lowercase letters, numbers, and random characters. (A tab character might not be a wise choice, depending on what kinds of computers you'll be logging in from.) There are many software packages that can generate random passwords for you; search the Internet for these utilities. In general, just use common sense: don't pick a password that is someone's birthday, a common phrase, something found on your desk, or anything that is easily associated with you. A password like “secure1” or any other password you see in print or online is also bad.

Removing users is not difficult at all. Just run userdel with the name of the account to remove. You should verify that the user is not logged in, and that no processes are running as that user. Also, remember that once you've deleted the user, all of that user's password information is gone permanently.

# userdel jellyd

This command removes that annoying jellyd user from your system. Good riddance! :) The user is removed from the /etc/passwd, /etc/shadow, and /etc/group files, but doesn't remove the user's home directory.

If you'd wanted to remove the home directory as well, you would instead use this command:

# userdel -r jellyd

Temporarily disabling an account will be covered in the next section on passwords, since a temporary change involves changing the user's password. Changing other account information is covered in Section 12.1.3.

The programs to add and remove groups are very simple. groupadd will just add another entry to the /etc/group file with a unique group ID, while groupdel will remove the specified group. It is up to you to edit /etc/group to add users to a specific group. For example, to add a group called cvs:

# groupadd cvs

And to remove it:

# groupdel cvs

12.1.2 Changing Passwords

The passwd program changes passwords by modifying the /etc/shadow file. This file holds all the passwords for the system in an encrypted format. In order to change your own password, you would type:

% passwd
Changing password for chris
Old password:
Enter the new password (minumum of 5, maximum of 127 characters)
Please use a combination of upper and lower case letters and numbers.
New password:

As you can see, you are prompted to enter your old password. It won't appear on the screen as you type it, just like when you log in. Then, you are prompted to enter the new password. passwd performs a lot of checks on your new password, and it will complain if your new password doesn't pass its checks. You can ignore its warnings if you want. You will be prompted to enter your new password a second time for confirmation.

If you are root, you can also change another user's password:

# passwd ted

You will then have to go through the same procedure as above, except that you won't have to enter the user's old password. (One of the many benefits of being root...)

If needed, you can also temporarily disable an account, and reenable it at a later time if needed. Both disabling an account and reenabling an account can be done with passwd. To disable an account, do the following as root:

# passwd -l david

This will change david's password to something that can never match any encrypted value. You would reenable the account by using:

# passwd -u david

Now, david's account is back to normal. Disabling an account might be useful if the user doesn't play by the rules you've set up on your system, or if they've exported a very large copy of xeyes(1) to your X desktop.

12.1.3 Changing User Information

There are two pieces of information that users can change at any time: their shell and their finger information. Slackware Linux uses chsh (change shell) and chfn (change finger) to modify these values.

A user can pick any shell that is listed in the /etc/shells file. For most people, /bin/bash will do just fine. Others might be familiar with a shell found on their system at work or school and want to use what they already know. To change your shell, use chsh:

% chsh
Password:
Changing the login shell for chris
Enter the new value, or press return for the default
        Login Shell [/bin/bash]:

After entering your password, enter the full path to the new shell. Make sure that it's listed in the /etc/shells(5) file first. The root user can also change any user's shell by running chsh with a username as the argument.

The finger information is the optional information such as your full name, phone numbers, and room number. This can be changed using chfn, and follows the same procedure as it did during account creation. As usual, root can change anyone's finger information.

13.3.1 host

host(1) can do this for us. host is used to map names to IP addresses. It is a very quick and simple utility without a lot of functions.

% host www.slackware.com
www.slackware.com is an alias for slackware.com.
slackware.com has address 64.57.102.34

But let's say for some reason we want to map an IP address to a domain name; what then?

13.3.2 nslookup

nslookup is a tried and true program that has weathered the ages. nslookup has been deprecated and may be removed from future releases. There is not even a man page for this program.

% nslookup 64.57.102.34
Note:  nslookup is deprecated and may be removed from future releases.
Consider using the `dig' or `host' programs instead.  Run nslookup with
the `-sil[ent]' option to prevent this message from appearing.
Server:         192.168.1.254
Address:        192.168.1.254#53

Non-authoritative answer:
www.slackware.com       canonical name = slackware.com.
Name:   slackware.com
Address: 64.57.102.34

13.3.3 dig

The meanest dog in the pound, the domain information groper, dig(1) for short, is the go-to program for finding DNS information. dig can grab just about anything from a DNS server including reverse lookups, A, CNAME, MX, SP, and TXT records. dig has many command line options and if you're not familiar with it you should read through it's extensive man page.

% dig @192.168.1.254 www.slackware.com mx

; <<>> DiG 9.2.2 <<>> @192.168.1.254 www.slackware.com mx
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 26362
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 2, ADDITIONAL: 2

;; QUESTION SECTION:
;www.slackware.com.             IN      MX

;; ANSWER SECTION:
www.slackware.com.      76634   IN      CNAME   slackware.com.
slackware.com.          86400   IN      MX      1 mail.slackware.com.

;; AUTHORITY SECTION:
slackware.com.          86400   IN      NS      ns1.cwo.com.
slackware.com.          86400   IN      NS      ns2.cwo.com.

;; ADDITIONAL SECTION:
ns1.cwo.com.            163033  IN      A       64.57.100.2
ns2.cwo.com.            163033  IN      A       64.57.100.3

;; Query time: 149 msec
;; SERVER: 192.168.1.254#53(192.168.1.254)
;; WHEN: Sat Nov  6 16:59:31 2004
;; MSG SIZE  rcvd: 159

This should give you an idea how dig works. “@192.168.1.254” specifies the dns server to use. “www.slackware.com” is the domain name I am performing a lookup on, and “mx” is the type of lookup I am performing. The above query tells me that e-mail to www.slackware.com will instead be sent to mail.slackware.com for delivery.

13.5.1 The other use of telnet

Now that we have convinced you not to use the telnet protocol anymore to log into a remote machine, we'll show you a couple of useful ways to use telnet.

You can also use the telnet command to connect to a host on a certain port.

% telnet <hostname> [port]

This can be quite handy when you quickly need to test a certain service, and you need full control over the commands, and you need to see what exactly is going on. You can interactively test or use an SMTP server, a POP3 server, an HTTP server, etc. this way.

In the next figure you'll see how you can telnet to a HTTP server on port 80, and get some basic information from it.

% telnet store.slackware.com 80
Trying 69.50.233.153...
Connected to store.slackware.com.
Escape character is '^]'.
HEAD / HTTP/1.0

HTTP/1.1 200 OK
Date: Mon, 25 Apr 2005 20:47:01 GMT
Server: Apache/1.3.33 (Unix) mod_ssl/2.8.22 OpenSSL/0.9.7d
Last-Modified: Fri, 18 Apr 2003 10:58:54 GMT
ETag: "193424-c0-3e9fda6e"
Accept-Ranges: bytes
Content-Length: 192
Connection: close
Content-Type: text/html

Connection closed by foreign host.
%

You can do the same for other plain-text protocols, as long as you know what port to connect to, and what the commands are.

13.7.1 pine

pine(1) is not elm. Or so the saying goes. The University of Washington created their program for Internet news and email out of a need for an easy mail reader for their students. pine is one of the most popular email clients in use today and is available for nearly every flavor of Unix and even Windows.

You will see a menu of commands and a row of command keys at the bottom. pine is indeed a complex program, so we will not discuss every feature about it here.

To see what's in your inbox, type i. Your messages are listed with their date, author, and subject. Highlight the message you want and press enter to view it. Pressing r will start a reply to the message. Once you have written the response, type Ctrl+X to send it. You can press i to get back to the message listing.

If you want to delete a message, press d. It will mark the highlighted message for deletion. pine deletes the mail when you exit the program. pine also lets you store your mail in folders. You can get a listing of folders by pressing l. At the message listing, press s to save it to another folder. It will ask for the folder name to write the message to.

pine offers many, many features; you should definitely have a look at the man page for more information. It will contain the latest information about the program.

13.7.2 elm

elm(1) is another popular text-based email client. Though not quite as user friendly as pine, it's definitely been around a lot longer.

By default, you are placed in your inbox. The messages are listed with the message number, date, sender, and subject. Use the arrow keys to highlight the message you want. Press Enter to read the message.

To compose a new message, type m at the main screen. The d key will flag a message for deletion. And the r key will reply to the current message you are reading. All of these keys are displayed at the bottom of the screen with a prompt.

The man page discusses elm in more detail, so you will probably want to consult that before using elm.

13.7.3 mutt

“All mail clients suck. This one just sucks less.” mutt's original interface was based on elm with added features found in other popular mailclients, resulting in a hybrid mutt.

Some of mutt's features include:

• color support

• message threading

• MIME and PGP/MIME support

• pop3 and imap support

• support for multiple mailbox formats (mbox, MMDF, MH, maildir)

• highly customizable

if you're looking for a mail client that will let you be in total control over everything, then you will like mutt. all the default settings can be customized, keybindings can be changed. if you like to add a macro, you can.

you probably want to take a look at the muttrc manpage, which will tell you how to configure everything. or take a look at the included example muttrc file.

13.7.4 nail

nail(1) is a command line driven mail client. It is very primitive and offers pretty much nothing in the way of user interfaces. However, mailx is handy for times when you need to quickly mail something, scripting a bulk mailer, testing your MTA installation or something similar. Note that Slackware creates symbolic links to nail at /usr/bin/mail and /usr/bin/mailx. Any of these three commands executes the same program. In fact, you will most likely see nail referred to as mail.

The basic command line is:

% mailx <subject> <to-addr>

mailx reads the message body from standard input. So you can cat a file into this command to mail it, or you can just type text and hit Ctrl+D when finished with the message.

Here is an example of mailing a program source file to another person.

% cat randomfunc.c | mail -s "Here's that function" asdf@example.net

The man page explains more of what nail can do, so you will probably want to have a look at that before using it.

13.8.1 lynx

lynx(1) is a text-based web browser. It is a very quick way of looking up something on the Internet. Sometimes graphics just get in the way if you know exactly what you're after.

To start lynx, just type lynx at the prompt:

% lynx

You may want to specify a site for lynx to open to:

% lynx http://www.slackware.com

lynx prints the command keys and what they do at the bottom of the screen. The up and down arrow keys move around the document, Enter selects the highlighted link, and the left arrow goes back to the previous page. Typing d will download the currently selected file. The g command brings up the Go prompt, where you can give lynx a URL to open.

There are many other commands in lynx. You can either consult the man page, or type h to get the help screen for more information.

13.8.2 links

Just like lynx, links is a textmode web browser, where you do all the navigation using the keyboard. However, when you press the Esc key, it will activate a very convenient pulldown menu on the top of the screen. This makes it very easy to use, without having to learn all the keyboard shortcuts. People who do not use a text browser every day will appreciate this feature.

links seems to have better support for both frames and tables, when compared to lynx.

13.8.3 wget

wget(1) is a command line utility that will download files from a specified URL. While not an actual web-browser, wget is used primarily to grab whole or partial web sites for offline viewing, or for fast download of single files from HTTP or FTP servers instead. The basic syntax is:

% wget <url>

You can also pass options. For example, this will download the Slackware web site:

% wget --recursive http://www.slackware.com

wget will create a www.slackware.com directory and store the files in there, just as the site does.

wget can also download files from FTP sites; just specify an FTP URL instead of an HTTP one.

% wget ftp://ftp.gnu.org/gnu/wget/wget-1.8.2.tar.gz
--12:18:16--  ftp://ftp.gnu.org/gnu/wget/wget-1.8.2.tar.gz
           => `wget-1.8.2.tar.gz'
Resolving ftp.gnu.org... done.
Connecting to ftp.gnu.org[199.232.41.7]:21... connected.
Logging in as anonymous ... Logged in!
==> SYST ... done.   ==> PWD ... done.
==> TYPE I ... done. ==> CWD /gnu/wget ... done.
==> PORT ... done.   ==> RETR wget-1.8.2.tar.gz ... done.
Length: 1,154,648 (unauthoritative)

100%[==================================>] 1,154,648     209.55K/s    ETA 00:00

12:18:23 (209.55KB/s) - `wget-1.8.2.tar.gz' saved [1154648]

wget has many more options, which make it nice for site specific scripts (web site mirroring and so forth). The man page should be consulted for more information.

13.9.1 ftp

To connect to an FTP server, simply run the ftp(1) command and specify the host:

% ftp <hostname> [port]

If the host is running an FTP server, it will ask for a username and password. You can log in as yourself or as “anonymous”. Anonymous FTP sites are very popular for software archives. For example, to get Slackware Linux via FTP, you must use anonymous FTP.

Once connected, you will be at the ftp> prompt. There are special commands for FTP, but they are similar to other standard commands. The following shows some of the basic commands and what they do:

You can also use some of the following commands which are quite self-explanatory: chmod, delete, rename, rmdir. For a complete list of all commands and their meaning, just type help or ? and you'll see a complete listing on screen.

FTP is a fairly simple program to use, but lacks the user interface that many of us are used to nowadays. The man page discusses some of the command line options for ftp(1).

ftp> ls *.TXT
200 PORT command successful.
150 Opening ASCII mode data connection for /bin/ls.
-rw-r--r--   1 root     100         18606 Apr  6  2002 BOOTING.TXT
-rw-r--r--   1 root     100         10518 Jun 13  2002 COPYRIGHT.TXT
-rw-r--r--   1 root     100           602 Apr  6  2002 CRYPTO_NOTICE.TXT
-rw-r--r--   1 root     100         32431 Sep 29 02:56 FAQ.TXT
-rw-r--r--   1 root     100        499784 Mar  3 19:29 FILELIST.TXT
-rw-r--r--   1 root     100        241099 Mar  3 19:12 PACKAGES.TXT
-rw-r--r--   1 root     100         12339 Jun 19  2002 README81.TXT
-rw-r--r--   1 root     100         14826 Jun 17  2002 SPEAKUP_DOCS.TXT
-rw-r--r--   1 root     100         15434 Jun 17  2002 SPEAK_INSTALL.TXT
-rw-r--r--   1 root     100          2876 Jun 17  2002 UPGRADE.TXT
226 Transfer complete.
ftp> tick
Tick counter printing on (10240 bytes/tick increment).
ftp> get README81.TXT
local: README81.TXT remote: README81.TXT
200 PORT command successful.
150 Opening BINARY mode data connection for README81.TXT (12339 bytes).
Bytes transferred: 12339
226 Transfer complete.
12339 bytes received in 0.208 secs (58 Kbytes/sec)

13.9.2 ncftp

ncftp(1) (pronounced "Nik-F-T-P") is an alternative to the traditional ftp client that comes with Slackware. It is still a text-based program, but offers many advantages over ftp, including:

• Tab completion

• Bookmarks file

• More liberal wildcard uses

• Command history

By default, ncftp will try to log in anonymously to the server you specify. You can force ncftp to present a login prompt with the “-u” option. Once logged in, you can use the same commands as in ftp, only you'll notice a nicer interface, one that works more like bash.

ncftp /pub/linux/slackware > cd slackware-current/
Please read the file README81.TXT
  it was last modified on Wed Jun 19 16:24:21 2002 - 258 days ago
CWD command successful.
ncftp ...ware/slackware-current > ls
BOOTING.TXT               FAQ.TXT                   bootdisks/
CHECKSUMS                 FILELIST.TXT              extra/
CHECKSUMS.asc             GPG-KEY                   isolinux/
CHECKSUMS.md5             PACKAGES.TXT              kernels/
CHECKSUMS.md5.asc         PRERELEASE_NOTES          pasture/
COPYING                   README81.TXT              rootdisks/
COPYRIGHT.TXT             SPEEKUP_DOCS.TXT          slackware/
CRYPTO_NOTICE.TXT         SPEEK_INSTALL.TXT         source/
CURRENT.WARNING           Slackware-HOWTO
ChangeLog.txt             UPGRADE.TXT
ncftp ...ware/slackware-current > get README81.TXT
README81.TXT:                                           12.29 kB  307.07 kB/s

13.10.1 wall

wall(1) is a quick way to write a message to the users on a system. The basic syntax is:

% wall [file]

This will result in the contents of [file] being displayed on the terminals of all currently logged in users. If you don't specify a file, wall will read from standard input, so you can just type your message, and end with Ctrl+d.

wall doesn't have many features, and apart from letting your users know that you're about to do some serious maintenance to the system, or even reboot it, so they have time to save their work and log off :)

13.10.2 talk

talk(1) allows two users to chat. It splits the screen in half, horizontally. To request a chat with another user, use this command:

% talk <person> [ttyname]

If you specify just a username, the chat request is assumed to be local, so only local users are queried. The ttyname is required if you want to ring a user on a specific terminal (if the user is logged in more than once). The required information for talk can be obtained from the w(1) command.

talk can also ring users on remote hosts. For the username you simply specify an email address. talk will try to contact that remote user on that host.

talk is somewhat limited. It only supports two users and is half-duplex.

13.10.3 ytalk

ytalk(1) is a backwards compatible replacement for talk. It comes with Slackware as the ytalk command. The syntax is similar, but has a few differences:

% ytalk <username>[#ttyname]

The username and terminal are specified the same as under talk, except you must put them together with the hash mark (#).

ytalk offers several advantages:

• It supports more than two users.

• A menu of options that can be brought up anytime with Esc.

• You can shell out while still in the talk session.

• Plus more...

If you're a server administrator, you'll want to make sure that the ntalk port is enabled in /etc/inetd.conf. ytalk needs that to work properly.

14.1.1 Services started from inetd

A lot of the daemons that come with Slackware are run from inetd(8). inetd is a daemon that listens on all of the ports used by services configured to be started by it and spawns an instance of the relevant daemon when a connection attempt is made. Daemons started from inetd can be disabled by commenting out the relevant lines in /etc/inetd.conf. To do this, open this file in your favorite editor (e.g. vi) and you should see lines similar to this:

telnet stream  tcp     nowait  root    /usr/sbin/tcpd  in.telnetd

You can disable this service, and any others you don't need, by commenting them out (i.e. adding a # (hash) symbol to the beginning of the line). The above line would then become:

#telnet stream  tcp     nowait  root    /usr/sbin/tcpd  in.telnetd

After inetd has been restarted, this service will be disabled. You can restart inetd with the command:

# kill -HUP $(cat /var/run/inetd.pid)

14.1.2 Services started from init scripts

The rest of the services started when the machine starts are started from the init scripts in /etc/rc.d/. These can be disabled in two different ways, the first being to remove the execute permissions on the relevant init script and the second being to comment out the relevant lines in the init scripts.

For example, SSH is started by its own init script at /etc/rc.d/rc.sshd. You can disable this using:

# chmod -x /etc/rc.d/rc.sshd

For services that don't have their own init script, you will need to comment out the relevant lines in the init scripts to disable them. For example, the portmap daemon is started by the following lines in /etc/rc.d/rc.inet2:

# This must be running in order to mount NFS volumes.
# Start the RPC portmapper:
if [ -x /sbin/rpc.portmap ]; then
  echo "Starting RPC portmapper:  /sbin/rpc.portmap"
  /sbin/rpc.portmap
fi
# Done starting the RPC portmapper.

This can be disabled by adding # symbols to the beginnings of the lines that don't already start with them, like so:

# This must be running in order to mount NFS volumes.
# Start the RPC portmapper:
#if [ -x /sbin/rpc.portmap ]; then
#  echo "Starting RPC portmapper:  /sbin/rpc.portmap"
#  /sbin/rpc.portmap
#fi
# Done starting the RPC portmapper.

These changes will only take effect after either a reboot or changing from and back to runlevel 3 or 4. You can do this by typing the following on the console (you will need to log in again after changing to runlevel 1):

# telinit 1
# telinit 3

14.2.1 iptables

iptables is the packet filtering configuration program for Linux 2.4 and above. The 2.4 kernel (2.4.5, to be exact) was first introduced into Slackware (as an option) in version 8.0 and was made the default in Slackware 8.1. This section only covers the basics of its usage and you should check http://www.netfilter.org/ for more details. These commands can be entered into /etc/rc.d/rc.firewall, which has to be set as executable for these rules to take effect at startup. Note that incorrect iptables commands can essentially lock you out of your own machine. Unless you are 100% confident in your skills, always ensure you have local access to the machine.

The first thing most people should do is set the default policy for each inbound chain to DROP:

# iptables -P INPUT DROP
# iptables -P FORWARD DROP

When everything is denied, you can start allowing things. The first thing to allow is any traffic for sessions which are already established:

# iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

So as not to break any applications that communicate using the loopback address, it is usually wise to add a rule like this:

# iptables -A INPUT -s 127.0.0.0/8 -d 127.0.0.0/8 -i lo -j ACCEPT

This rules allows any traffic to and from 127.0.0.0/8 (127.0.0.0 - 127.255.255.255) on the loopback (lo) interface. When creating rules, it is a good idea to be as specific as possible, to make sure that your rules do not inadvertently allow anything evil. That said, rules that allow too little mean more rules and more typing.

The next thing to do would be to allow access to specific services running on your machine. If, for example, you wanted to run a web server on your machine, you would use a rule similar to this:

# iptables -A INPUT -p tcp --dport 80 -i ppp0 -j ACCEPT

This will allow access from any machine to port 80 on your machine via the ppp0 interface. You may want to restrict access to this service so that only certain machines can access it. This rule allows access to your web service from 64.57.102.34:

# iptables -A INPUT -p tcp -s 64.57.102.34 --dport 80 -i ppp0 -j ACCEPT

Allowing ICMP traffic can be useful for diagnostic purposes. To do this, you would use a rule like this:

# iptables -A INPUT -p icmp -j ACCEPT

Most people will also want to set up Network Address Translation (NAT) on their gateway machine, so that other machines on their network can access the Internet through it. You would use the following rule to do this:

# iptables -t nat -A POSTROUTING -o ppp0 -j MASQUERADE

You will also need to enable IP forwarding. You can do this temporarily, using the following command:

# echo 1 > /proc/sys/net/ipv4/ip_forward

To enable IP forwarding on a more permanent basis (i.e. so that the change is kept after a reboot), you will need to open the file /etc/rc.d/rc.inet2 in your favorite editor and change the following line:

IPV4_FORWARD=0

...to this:

IPV4_FORWARD=1

For more information on NAT, see the NAT HOWTO.

14.2.2 tcpwrappers

tcpwrappers controls access to daemons at the application level, rather than at the IP level. This can provide an extra layer of security at times when IP-level access controls (e.g. Netfilter) are not functioning correctly. For example, if you recompile the kernel but forget to include iptables support, your IP level protection will fail but tcpwrappers will still help protect your system.

Access to services protected by tcpwrappers can be controlled using /etc/hosts.allow and /etc/hosts.deny.

The majority of people would have a single line in their /etc/hosts.deny file to deny access to all daemons by default. This line would be:

ALL : ALL

When this is done, you can concentrate on allowing access to services for specified hosts, domains, or IP ranges. This can be done in the /etc/hosts.allow file, which follows the same format.

A lot of people would start by accepting all connections from localhost. This can be achieved using:

ALL : 127.0.0.1

To allow access to SSHd from 192.168.0.0/24, you could use either of the following rules:

sshd : 192.168.0.0/24
sshd : 192.168.0.

It is also possible to restrict access to hosts in certain domains. This can be done using the following rule (note that this relies on the reverse DNS entry for the connecting host being trustworthy, so I would recommand against its use on Internet-connected hosts):

sshd : .slackware.com

14.3.1 slackware-security mailing list

Whenever a security problem affects Slackware, an email is sent to all subscribers to the slackware-security@slackware.com mailing list. Reports are sent out for vulnerabilities of any part of Slackware, apart from the software in /extra or /pasture. These security announcement emails include details on obtaining updated versions of Slackware packages or work-arounds, if any.

Subscribing to Slackware mailing lists is covered in Section 2.2.2.

14.3.2 The /patches directory

Whenever updated packages are released for a version of Slackware (usually only to fix a security problem, in the case of already released Slackware versions), they are placed in the /patches directory. The full path to these patches will depend on the mirror you are using, but will take the form /path/to/slackware-x.x/patches/.

Before installing these packages, it is a good idea to verify the md5sum of the package. md5sum(1) is a commandline utility that creates a “unique” mathematical hash of the file. If a single bit of the file has been changed, it will generate a different md5sum value.

% md5sum package-<ver>-<arch>-<rev>.tgz
6341417aa1c025448b53073a1f1d287d  package-<ver>-<arch>-<rev>.tgz

You should then check this against the line for the new package in the CHECKSUMS.md5 file in the root of the slackware-$VERSION directory (also in the /patches directory for patches) or in the email to the slackware-security mailing list.

If you have a file with the md5sum values in it, you can source it instead with the -c option to md5sum.

# md5sum -c CHECKSUMS.md5
./ANNOUNCE.10_0: OK
./BOOTING.TXT: OK
./COPYING: OK
./COPYRIGHT.TXT: OK
./CRYPTO_NOTICE.TXT: OK
./ChangeLog.txt: OK
./FAQ.TXT: FAILED

As you can see, any files that md5sum evaluates as correct are listed “OK” while files that fail are labelled “FAILED”. (Yes, this was an insult to your intelligence. Why do you put up with me?)

16.2.1 Command Mode

You are first placed into command mode. From this mode, you cannot directly enter text or edit what is already there. However, you can manipulate the text, search, quit, save, load new files, and more. This is intended only to be an introduction to the command mode. For a description of the various commands, see Section 16.7.

Probably the most often used command in command mode is changing to insert mode. This is accomplished by hitting the i key. The cursor changes shapes, and -- INSERT -- is displayed at the bottom of the screen (note that this does not happen in all clones of vi). From there, all your keystrokes are entered into the current buffer and are displayed to the screen. To get back into command mode, hit the ESCAPE key.

Command mode is also where you move around in the file. On some systems, you can use the arrow keys to move around. On other systems, you may need to use the more traditional keys of “hjkl”. Here is a simple listing of how these keys are used to move around:

Simply press a key to move. As you will see later, these keys can be combined with a number to move much more efficiently.

Many of the commands that you will use in command mode begin with a colon. For example, quitting is :q, as discussed earlier. The colon simply indicates that it is a command, while the “q” tells vi to quit. Other commands are an optional number, followed by a letter. These commands do not have a colon before them, and are generally used to manipulate the text.

For example, deleting one line from a file is accomplished by hitting dd. This will remove the line that the cursor is on. Issuing the command 4dd would tell vi to remove the line that the cursor is on and the three after that. In general, the number tells vi how many times to perform the command.

You can combine a number with the movement keys to move around several characters at a time. For example, 10k would move up ten lines on the screen.

Command mode can also be used to cut and paste, insert text, and read other files into the current buffer. Copying text is accomplished with the y key (y stands for yank). Copying the current line is done by typing yy, and this can be prefixed with a number to yank more lines. Then, move to the location for the copy and hit p. The text is pasted on the line after the current one.

Cutting text is done by typing dd, and p can be used to paste the cut text back into the file. Reading in text from another file is a simple procedure. Just type :r, followed by a space and the file name that contains the text to be inserted. The file's contents will be pasted into the current buffer on the line after the cursor. More sophisticated vi clones even contain filename completion similar to the shell's.

The final use that will be covered is searching. Command mode allows for simple searching, as well as complicated search-and-replace commands that make use of a powerful version of regular expressions. A complete discussion of regular expressions is beyond the scope of this chapter, so this section will only cover simple means of searching.

A simple search is accomplished by hitting the / key, followed by the text that you are searching for. vi will search forward from the cursor to the end of the file for a match, stopping when it finds one. Note that inexact matches will cause vi to stop as well. For example, a search for “the” will cause vi to stop on “then”, “therefore”, and so on. This is because all of those words do match “the”.

After vi has found the first match, you can continue on to the next match simply by hitting the / key followed by enter. You can also search backwards through the file by replacing the slash with the ? key. For example, searching backwards through the file for “the” would be accomplished by typing ?the.

16.2.2 Insert Mode

Inserting and replacing text is accomplished in insert mode. As previously discussed, you can get into insert mode by hitting i from command mode. Then, all text that you type is entered into the current buffer. Hitting the ESCAPE key takes you back into command mode.

Replacing text is accomplished in several ways. From command mode, hitting r will allow you to replace the one character underneath the cursor. Just type the new character and it will replace the one under the cursor. You will then be immediately placed back into command mode. Hitting R allows you to replace as many characters as you'd like. To get out of this replacement mode, just hit ESCAPE to go back into command mode.

There is yet another way to toggle between insertion and replacement. Hitting the INSERT key from command mode will take you into insert mode. Once you are in insert mode, the keyboard's INSERT key serves as a toggle between insert and replace. Hitting it once will allow you to replace. Hitting it once more will once again allow you to insert text.

17.1.1 Command Keys

As mentioned above, Emacs uses Control and Alt combinations for commands. The usual convention is to write these with C-letter and M-letter, respectively. So C-x means Control+x, and M-x means Alt+x. (The letter M is used instead of A because originally the key was not the Alt key but the Meta key. The Meta key has all but disappeared from computer keyboards, and in Emacs the Alt key has taken over its function.)

Many Emacs commands consist of sequences of keys and key combinations. For example, C-x C-c (that is Control-x followed by Control-c ) quits Emacs, C-x C-s saves the current file. Keep in mind that C-x C-b is not the same as C-x b. The former means Control-x followed by Control-b, while the latter means Control-x followed by just 'b'.

17.3.1 Opening files

To open a file in Emacs, type

C-x C-f

Emacs will ask you for the name of the file, filling in some default path for you (which is usually ~/ ). After you type the filename (you can use Tab completion) and hit ENTER , Emacs will open the file in a new buffer and display that buffer on the screen.

Emacs will automatically create a new buffer, it will not load the file into the current buffer.

In order to create a new file in emacs, you cannot just go typing right away. You first have to create a buffer for it, and come up with a filename. You do this by typing C-x C-f and typing a filename, just as if you were opening an existing file. Emacs will notice that the file you typed doesn't exist, and will create a new buffer and report “(New file)” in the minibuffer.

When you type C-x C-f and then enter a directory name instead of a filename, Emacs will create a new buffer in which you will find a list of all the files in that directory. You can move the cursor to the file that you are looking for and type , and Emacs will open it. (There are in fact a lot more actions you can perform here, such as deleting, renaming and moving files, etc. Emacs is now in dired-mode, which is basically a simple file manager.)

When you have typed C-x C-f and suddenly change your mind, you can type C-g to cancel the action. C-g works almost everywhere where you want to cancel an action or command that you've started but don't want to finish.

17.5.1 Quitting Emacs

When you are done with Emacs altogether, you can type

C-x C-c

This quits Emacs. If you have any unsaved files, Emacs will tell you so, and ask if you want to save them each in turn. If you answer no to any of these, Emacs will ask for one final confirmation and then quit.

18.2.1 pkgtool

pkgtool(8) is a menu-driven program that allows installation and removal of packages. The main menu is shown in Figure 18-1.

Installation is offered from the current directory, another directory, or from floppy disks. Simply select the installation method you want and pkgtool will search that location for valid packages to install.

You may also view a list of installed packages, as shown in Figure 18-2.

If you want to remove packages, select the remove option and you will be presented with a checklist of all the installed packages. Flag the ones you want to remove and select OK. pkgtool will remove them.

Some users prefer this utility to the command line utilities. However, it should be noted that the command line utilities offer many more options. Also, the ability to upgrade packages is only offered through the command line utilities.

18.2.2 installpkg

installpkg(8) handles installation of new packages on the system. The syntax is as follows:

# installpkg option package_name

Three options are provided for installpkg. Only one option can be used at a time.

If you pass the ROOT environment variable before installpkg, that path will be used for the root directory. This is useful for setting up new drives for your root directory. They will typically be mounted to /mnt or something other than /.

The installed package database entry is stored in /var/log/packages. The entry is really just a plain text file, one for each package. If the package has a postinstallation script, it is written to /var/log/scripts/.

You may specify several packages or use wildcards for the package name. Be advised that installpkg will not tell you if you are overwriting an installed package. It will simply install right on top of the old one. If you want to ensure that old files from the previous package are safely removed, use upgradepkg.

18.2.3 removepkg

removepkg(8) handles removing installed packages from the system. The syntax is as follows:

# removepkg option package_name

Four options are provided for removepkg. Only one option may be used at a time.

If you pass the ROOT environment variable before removepkg, that path will be used for the root directory. This is useful for setting up new drives for your root directory. They will typically be mounted to /mnt or something other than /.

removepkg looks at the other installed packages and only removes files unique to the package you specify. It will also scan the postinstallation script for the specified package and remove any symbolic links that were created by it.

During the removal process, a status report is displayed. After the removal, the package database entry is moved to /var/log/removed_packages and the postinstallation script is moved to /var/log/removed_scripts.

Just as with installpkg, you can specify several packages or use wildcards for the package name.

18.2.4 upgradepkg

upgradepkg(8) will upgrade an installed Slackware package. The syntax is as follows:

# upgradepkg package_name

or

# upgradepkg old_package_name%new_package_name

upgradepkg works by first installing the new package and then removing the old package so that old files are no longer around on the system. If the upgraded package name has changed, use the percent sign syntax to specify the old package (the one that is installed) and the new package (the one you are upgrading it to).

If you pass the ROOT environment variable before upgradepkg, that path will be used for the root directory. This is useful for setting up new drives for your root directory. They will typically be mounted to /mnt or something other than /.

upgradepkg is not flawless. You should always back up your configuration files. If they get removed or overwritten, you'll want a copy of the originals for any needed repair work.

Just as with installpkg and removepkg, you can specify several packages or use wildcards for the package name.

18.2.5 rpm2tgz/rpm2targz

The Red Hat Package Manager is a popular packaging system available today. Many software distributors are offering their products in RPM format. Since this is not our native format, we do not recommend people rely on them. However, some things are only available as an RPM (even the source).

We provide a program that will convert RPM packages to our native .tgz format. This will allow you to extract the package (perhaps with explodepkg) to a temporary directory and examine its contents.

The rpm2tgz program will create a Slackware package with a .tgz extension, while rpm2targz creates an archive with a .tar.gz extension.

18.3.1 explodepkg

explodepkg(8) will do the same thing that installpkg does to extract the package, but it doesn't actually install it and it doesn't record it in the packages database. It simply extracts it to the current directory.

If you look at the Slackware source tree, you will see how we use this command for “framework” packages. These packages contain a skeleton of what the final package will look like. They hold all the necessary filenames (zero-length), permissions, and ownerships. The build script will cat the package contents from the source directory to the package build directory.

18.3.2 makepkg

makepkg(8) will package up the current directory into a valid Slackware package. It will search the tree for any symbolic links and add a creation block to the postinstallation script for creating them during the package install. It also warns of any zero-length files in the package tree.

This command is typically run after you have created your package tree.

18.3.3 SlackBuild Scripts

Slackware packages are built in many different ways by necessity. Not all software packages are written by their programmers to compile the same way. Many have compile time options that are not all included in the packages Slackware uses. Perhaps you need some of this functionality; you'll need to compile your own package then. Fortunately for many Slackware packages, you can find SlackBuild scripts in the package's source code.

So what is a SlackBuild script? SlackBuild scripts are executable shell scripts that you run as root to configure, compile, and create Slackware packages. You can freely modify these scripts in the source directory and run them to create your own versions of the default Slackware packages.

19.1.1 Advantages

• Does not require repartitioning of your hard disk.

• Great way to learn Slackware Linux without stumbling through the installation process.

19.1.2 Disadvantages

• Uses the DOS filesystem, which is slower than a native Linux filesystem.

• Will not work with Windows NT.

19.2.1 Installation

Once you've downloaded the necessary components, you'll need to extract the .ZIP file. Be sure to use a 32-bit unzipper. The size and filenames in the archive are too much for a 16-bit unzipper. Examples of 32-bit unzippers include WinZip and PKZIP for Windows.

ZipSlack is designed to be extracted directly to the root directory of a drive (such as C: or D:). A \LINUX directory will be created that contains the actual Slackware installation. You'll also find the files necessary to booting the system in that directory as well.

After you've extracted the files, you should have a \LINUX directory on the drive of your choosing (we'll use C: from here on).