Fedora Linux

successfully completed. If not, the user is informed and rpm aborts execution.

2. The RPM database is queried to see if any installation trigger scripts in other packages are triggered by the installation, and if so, they are executed.

3. The preinstallation script in the package is executed.

4. The package files are installed. Required directories are created, relocations are performed, and permissions and ownership are adjusted.

5. The postinstallation script in the package is executed.

6. If the operation being performed is not an upgrade or freshen, rpm exits because there isn't an older version of the package to uninstall.

7. The RPM database is queried to see if any uninstallation trigger scripts in other packages are triggered by the removal of the old package, and if so, they are executed.

8. The pre-uninstallation script in the package is executed.

9. If repackaging has been selected, the old package files and metadata are used to construct an RPM, which is placed in /var/spool/repackage .

10. The obsolete files from the old package are deleted.

11. The post-uninstallation script in the package is executed.

12. The RPM database is queried to see if any post-uninstallation trigger scripts in other packages are triggered by the removal of the old package, and if so, they are executed.

13. The RPM database is updated to reflect what was done during the transaction.

There are four opportunities for scripts to run. This permits configuration files to be backed up before new packages are installed, services to be stopped before upgrading and restarted after, and configuration data to be copied from the old to the new package. There are also three opportunities for trigger scripts to run.

Each RPM operation is called a transaction . All of the packages processed in one operation are called a transaction set ; this may include a large number of packages. For example, an update transaction could include dozens of packages processed at one time. In the RPM database, a transaction set identifier (TID) is used to tie together all of the packages processed in the same transaction set. The TID currently used is the time in seconds since the start of the 1970s (called a utime ).

5.2.3. What About...

5.2.3.1. ...installing multiple versions of a package?

It's possible, but it can create a lot of problems. The --force option is required, and it's probably best to relocate the second installation to avoid file conflicts:

# rpm -q httpd
httpd-2.0.54-10.2
# rpm -i --force httpd-2.0.54-10.i386.rpm  --relocate /=/var/compare/httpd- old
# rpm -q httpd
httpd-2.0.54-10.2
httpd-2.0.54-10

This will install the old version of httpd into /var/compare/httpd- old so that you can compare that installation with the current one.

To remove the packages, you'll either need to specify the full package name including the software and package version numbers (e.g., httpd-2.0.54-10 instead of httpd ) to delete one specific version, or use the --allmatches option to remove all versions:

# rpm -e httpd
error: 'httpd' specifies multiple packages
# rpm -e --allmatches httpd

5.2.4. Where Can I Learn More?

? Maximum RPM , Chapters 2 , 3 , and 4 : http://www.rpm.org/max-rpm- snapshot/ (somewhat out of date, but useful)

? The manpage for rpm

5.3. Using Repositories

RPM is a great package manager, but to really use packages efficiently, you'll need to use RPM along with a repository system so that your Fedora system can access remote libraries of software. Having access to the repository enables the automatic resolution of dependency issues, so that when you select a software package for installation, all required associated software is also installed automatically.

5.3.1. How Do I Do That?

Fedora uses the yum repository system. The apt system was used in earlier versions of Fedora and is still available, but most of the community's attention has shifted to yum, primarily because it supports multiple architecturesuseful when running 32-bit software (such as a 32-bit browser, for compatibility with closed-source plug-ins) on a 64-bit system.

5.3.1.1. Using yum from the command line

Using yum to install software is easy; just specify the install command and the package name you want installed as an argument:

# yum install abe
Setting up Install Process
Setting up repositories
updates-released 100% |=========================| 951 B 00:00