Chris Tyler - Fedora Linux

# rpm -ivh httpd-2.0.54-10.i386.rpm

Preparing... ########################################### [100%]

package httpd-2.0.54-10 is already installed

But if you add the --force option, the reinstallation will be successful:

# rpm -ivh --force httpd-2.0.54-10.i386.rpm

Preparing... ########################################### [100%]

1:httpd ########################################### [100%]

The httpd package normally places the DocumentRoot (start of the HTML document tree) in /var/www ; to change this to /usr/share/html , use the --relocate option:

# rpm -ivh --force --relocate /var/www=/usr/share/html/ httpd-2.0.54-10.i386.rpm

Preparing... ########################################### [100%]

1:httpd ########################################### [100%]

The change is recorded in the RPM database, so querying the database will show the actual, installed paths:

# rpm -ql httpd

/etc/httpd

/etc/httpd/conf

/etc/httpd/conf.d

/etc/httpd/conf.d/README

/etc/httpd/conf.d/welcome.conf

...(Many lines snipped)...

/usr/share/html/icons/world1.png

/usr/share/html/icons/world2.gif

/usr/share/html/icons/world2.png

Relocating files does not change configuration files, scripts, or programs that expect files to be located in particular locations. In the httpd example just shown, the Apache configuration files ( /etc/httpd/conf/httpd.conf plus module-specific files in /etc/httpd/conf.d/* ) must be edited by hand to reflect the new document root.

The options for erasing software are a subset of the options for installing and upgrading; the most useful options are listed in Table 5-4 .

Table 5-4. rpm package-removal (erase) options

RPMs are named using the pattern:

name - version - packagerelease . arch .rpm

in which:

name

The name of the software in the package.

version

The software's version number.

packagerelease

The package version number; if one version of the software has been packaged a few times (for example, with different file locations, scripts, triggers, or sample data), this number is incremented while the software version number is left unchanged.

arch

The architecture for which the package is compiled ( i386 , x86-64 , or PPC ). For packages that are not compiled (such as Perl, PHP, or bash scripts) or packages that contain only data (such as a font set), noarch is used; for source packages, the architecture is set to src .

rpm goes through many steps when performing an installation or upgrade/freshen:

1. The viability of the operation requested is analyzed. rpm tests the available disk space, dependencies, installed packages, and package integrity to ensure that the operation can be 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 ).

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: