- adduser userid
-
Creates a new userid, prompting for necessary
information (requires root privileges).
- alias name='command'
-
Defines name as an alias for the specified command.
- apropos keyword
-
Searches the manual pages for occurrences of the specified keyword
and prints short descriptions from the beginning of matching manual
pages.
- at time
- at -f file time
-
Executes commands entered via STDIN (or by using the alternative
form, the specified file) at the specified time. The time can be
specified in a variety of ways; for example, in hour and minute
format (hh:mm) or in hour, minute, month, day,
and year format (hh:mm
mm/dd/yy).
- atq
-
Displays descriptions of jobs pending via the at command.
- atrm job
-
Cancels execution of a job scheduled via the at command. Use the atq command to discover the identities of
scheduled jobs.
- bg
- bg jobs
-
Places the current job (or by using the
alternative form, the specified jobs) in the background, suspending
its execution so that a new user prompt appears immediately. Use the
jobs command to discover the
identities of background jobs.
- cal month year
-
Displays a calendar for the specified month of the specified year.
- cat files
-
Displays the contents of the specified files.
- cd
- cd directory
-
Changes the current working directory to the user's
home directory or the specified directory.
- chgrp group files
- chgrp -R group files
-
Changes the group of the specified files to the specified group. The
alternative form of the command operates recursively, changing the
group of subdirectories and files beneath a specified directory. The
group must be named in the /etc/groups file,
maintained by the newgroup command.
- chmod mode files
- chmod -R mode files
-
Changes the access mode of the specified files to the specified mode.
The alternative form of the command operates recursively, changing
the mode of subdirectories and files beneath a specified directory.
- chown userid files
- chown -R userid files
-
Changes the owner of the specified files to the specified
userid. The alternative form of the command
operates recursively, changing the owner of subdirectories and files
beneath a specified directory
- clear
-
Clears the terminal screen.
- cmp file1 file2
-
Compares two files, reporting all discrepancies. Unlike the diff command, cmp can compare multiple files and binary
files.
- cp file1 file2
- cp files directory
- cp -R files directory
-
Copies a file to another file or directory or copies a subdirectory
and all its files to another directory.
- date
- date date
-
Displays the current date and time or changes the system date and
time to the specified value, of the form
MMddhhmmyy or MMddhhmmyyyy.
- df
-
Displays the amount of free disk space on each mounted filesystem.
- diff file1 file2
-
Compares two files, reporting all discrepancies. Similar to the
cmp command, though the output
format differs.
- dmesg
-
Displays the messages resulting from the most recent system boot.
- du
- du directories
-
Displays the amount of disk space used by the current directory (or
the specified directories) and its (their) subdirectories.
- echo string
- echo -n string
-
Displays the specified text on the standard output stream. The
-n option causes omission of the
trailing newline character.
- fdformat device
-
Formats the media inserted in the specified floppy disk drive. The
command performs a low-level format only; it does not create a
filesystem. To create a filesystem, issue the mkfs command after formatting the media.
- fdisk device
-
Edits the partition table of the specified hard disk.
- fg
- fg jobs
-
Brings the current job (or the specified jobs) to the foreground.
- file files
-
Determines and prints a description of the type of each specified
file.
- find path -name pattern -print
-
Searches the specified path for
files with names matching the specified pattern (usually enclosed in
single quotes) and prints their names. The find command has many other arguments and
functions; see the online documentation.
- finger users
-
Displays descriptions of the specified users.
- free
-
Displays the amount of used and free system memory.
- ftp hostname
-
Opens an FTP connection to the specified host, allowing files to be
transferred. The FTP program provides subcommands for accomplishing
file transfers; see the online documentation.
- grep pattern files
- grep -i pattern files
- grep -n pattern files
- grep -v pattern files
-
Searches the specified files for text matching the specified pattern
(usually enclosed in single quotes) and prints matching lines. The
-i option specifies that matching is
performed without regard to case. The -n option specifies that each line of output is
preceded by the filename and line number. The -v option reverses the matching, causing
nonmatched lines to be printed.
- gzip files
- gunzip files
-
Expands or compresses the specified files. Generally, a compressed
file has the same name as the original file, followed by
.gz.
- head files
-
Displays the first several lines of each specified file.
- hostname
- hostname name
-
Displays (or sets) the name of the host.
- info
-
Launches the GNU Texinfo help system.
- init runlevel
-
Changes the system runlevel to the specified value (requires
root privileges).
- insmod module
-
Dynamically loads the specified module (requires
root privileges).
- ispell files
-
Checks the spelling of the contents of the specified files.
- jobs
-
Displays all background jobs.
- kill process_ids
- kill -l
- kill -signal process_ids
-
Kills the specified processes, prints a list of available signals, or
sends the specified processes the specified signal (given as a number
or name).
- killall program
- killall -signal program
-
Kills all processes that are instances of the specified program or
sends the specified signal to all processes that are instances of the
specified program.
- less file
-
Lets the user peruse a file too large to be displayed as a single
screen (page) of output. The less
command, which is more powerful than the more command, provides many subcommands that
let the user navigate the file. For example, the spacebar moves
forward one page, the b key moves
back one page, and the q key exits
the program.
- links URL
-
Views the specified web page.
- ln old new
- ln -s old new
-
Creates a hard (or soft) link associating a new name with an existing
file or directory.
- locate pattern
-
Locates files with names containing the specified pattern. Uses the
database maintained by the updatedb
command.
- lpq
-
Displays the entries of the print queue.
- lpr files
-
Displays the specified files.
- lprm job
-
Cancels printing of the specified print queue entries. Use lpq to determine the contents of the print
queue.
- ls
- ls files
- ls -a files
- ls -l files
- ls -lR files
-
Lists (nonhidden) files in the current directory or the specified
files or directories. The -a option
lists hidden files as well as nonhidden files. The -l option causes the list to include
descriptive information, such as file size and modification date. The
-R option recursively lists the
subdirectories of the specified directories.
- mail
-
Launches a simple mail client that permits sending and receiving
email messages.
- man title
- man section title
-
Displays the specified manpage.
- mkdir directories
- mkdir -p directories
-
Creates the specified directories. The -p option causes creation of any parent
directories needed to create a specified directory.
- mkfs -t type device
-
Creates a filesystem of the specified type (such as
ext3 or msdos) on the
specified device (requires
root privileges).
- mkswap device
-
Creates a Linux swap space on the specified hard disk partition
(requires root privileges).
- more file
-
Lets the user peruse a file too large to be displayed as a single
screen (page) of output. The more
command provides many subcommands that let the user navigate the
file. For example, the spacebar moves forward one page, the b key moves back one page, and the q key exits the program.
- mount
- mount device directory
- mount -o option -t type device directory
-
Displays the mounted devices or mounts the specified device at the
specified mount point (generally a subdirectory of
/mnt). The mount command consults
/etc/fstab to determine standard options
associated with a device. The command generally requires
root privileges. The -o option allows specification of a variety of
options, for example, ro for
read-only access. The -t option
allows specification of the filesystem type (for example,
ext3, msdos, or
iso9660, the filesystem type generally used for
CD-ROMs).
- mv paths target
-
Moves the specified files or directories to the specified target.
- newgroup group
-
Creates the specified group.
- passwd
- passwd user
-
Changes the current user's password or that of the
specified user (requires root privileges). The
command prompts for the new password.
- pico
- pico file
-
Launch pico to edit the specified
file, if any.
- ping -n ip_address
- ping host
-
Sends an echo request via TCP/IP to the specified host. A response
confirms that the host is operational.
- pr files
-
Formats the specified files for printing, by inserting page breaks
and so on. The command provides many arguments and functions.
- ps
- ps -aux
-
Displays the processes associated with the current
userid or displays a description of each
process.
- pwd
-
Displays the absolute path corresponding to the current working
directory.
- reboot
-
Reboots the system (requires root privileges).
- reset
-
Clears the terminal screen and resets the terminal status.
- rm files
- rm -f files
- rm -i files
- rm -if files
- rm -rf files
-
Deletes the specified files or (when the -r option is specified) recursively deletes all
subdirectories of the specified files and directories. The -f option suppresses confirmation; the
-i option causes the command to
prompt for confirmation. Because deleted files cannot generally be
recovered, the -f option should be
used only with extreme care, particularly when used by the
root user.
- rmdir directories
- rmdir -p directories
-
Deletes the specified empty directories or (when the -p option is specified) the empty directories
along the specified path.
- scp host1:file host2:
-
Copies file from host1 to
host2, via SSH.
- shutdown minutes
- shutdown -h minutes
- shutdown -r minutes
-
Shuts down the system after the specified number of minutes elapses
(requires root privileges). The -r option causes the system to be rebooted once
it has shut down. If the -r option
is absent, the system is halted and powered off; the -h option also halts and shuts down the system.
Alternatively, now can be used
instead of minutes, which forces an immediate
reboot or halt of the system.
- sleep time
-
Causes the command interpreter to pause for the specified number of
seconds.
- sort files
-
Sorts the specified files. The command has many useful arguments; see
the online documentation.
- split file
-
Splits a file into several smaller files. The command has many
arguments; see the online documentation.
- ssh host -l userid
-
Logs in to host via SSH, using the specified
userid.
- su
- su user
- su -
- su - user
-
Changes the current userid to
root or to the specified
userid (the latter requires
root privileges). The - option establishes a default environment for
the new userid.
- swapoff device
-
Disables use of the specified device for swapping (requires
root privileges).
- swapon device
-
Enables use of the specified device for swapping (requires
root privileges).
- sync
-
Completes all pending input/output
operations (requires root privileges).
- tail file
- tail -f file
- tail -n file
-
Displays the last several lines of the specified files. The
-f option causes the command to
continuously print additional lines as they are written to the file.
The -n option specifies the number
of lines to be printed.
- talk user
-
Launches a program that allows a chatlike dialog with the specified
user.
- tar cvf tar_file files
- tar zcvf tar_file files
-
Creates a tar file with the specified name, containing the specified
files and their subdirectories. The z option specifies that the tarfile will be
compressed.
- tar xvf tar_file
- tar zxvf tar_file
-
Extracts the contents of the specified tarfile. The z option specifies that the tarfile has been
compressed.
- telnet host
-
Opens a login session on the specified host.
- time
-
Times the execution of a job.
- top
-
Displays a display of system processes that's
continually updated until the user presses the q key.
- touch file
-
Changes file access time. If the specified file
does not exist, the command creates an empty (new) file.
- traceroute host
-
Uses echo requests to determine and print a network path to the host.
- umask mask
-
Specifies default permissions assigned to created directories and
files.
- umount device
-
Unmounts the specified filesystem (generally requires
root privileges).
- uname -a
-
Displays information about the system.
- unzip file
-
Unzips a compressed file.
- uptime
-
Displays the system uptime.
- w
-
Displays the current system users.
- wall
-
Displays a message to each user except those who've
disabled message reception. Type Ctrl-D to end the message.
- wc files
-
Displays the number of characters, words, and lines in the specified
files.
- who
-
Displays information about system users.
- zip file
-
Compresses the specified file.
