|Maximum RPM: Taking the Red Hat Package Manager to the Limit|
|Prev||Chapter 9. The Philosophy Behind RPM||Next|
While we are primarily concerned with RPM's advantages from the developer's point of view, it's worth looking at RPM from the user's standpoint for a moment. After all, if RPM makes life easier for your users, that can translate into lower support costs.
Probably the biggest headache for user and developer alike is the upgrade of an application, or worse yet, an entire operating system! RPM can make upgrading a one-step process. With one command, a new package can be installed, and the remnants of the old package removed.
Configuration files — nearly every application has them. They may go by different names, but they all control the behavior of their application. Users normally customize config files to their liking and would be upset if their customizations were lost during the installation, upgrade, or removal of a package.
RPM takes special care with a user's config files. By using MD5 checksums, RPM can determine what action is most appropriate with a config file. If a config file has been modified by the user and has to be replaced, it is saved. That way a user's modifications are never lost.
RPM uses a database to keep track of all files it installs. RPM's database provides other benefits, such as the wide variety of information that can be easily retrieved from it. RPM's query command makes it easy for users to quickly answer a number of questions, such as:
Where did this file come from? Is it part of a package?
What does this package do?
What packages are installed on my system?
These are just a few examples of the many ways RPM can provide information about one or more packages on a user's system.
Another way that RPM leverages the information stored in its database, is by providing an easy way to verify that a package is properly installed. With this capability, RPM makes it easy to determine, for example, what packages were damaged by a wildcard delete in /usr/bin. In addition, RPM's verification command can detect changes to file attributes, such as a file's permissions, ownership, and size.