What Is an RPM?

At the heart of Red hat is the RPM database. Among other things, this database tracks the version and location of each file in each RPM. The RPM database also maintains an MD5 checksum of each file. With the checksum, you can use the rpm -V package command to determine whether any file from that RPM package has changed. The RPM database makes adding, removing, and upgrading packages easy, because RPM knows which files to handle and where to put them.

RPM also manages conflicts between packages. For example, assume you have two different packages that use configuration files with the same name. Call the original configuration file /etc/someconfig.conf. You've already installed package X. If you the try to install package Y, RPM packages are dsigned to back up the original /etc/someconfig.conf file (with a file name like /etc/someconfig.conf.rpmsave) before installing package Y.

While RPM upgrades are supposed to preserve or save existing configuration files, there are no guarantees. It's best to back up all applicable configuration files before upgrading any associated RPM package.