By Andres Barcenas, System Administrator, PEER 1

Custom software installation on Red Hat Enterprise 3/4
The RedHat Package Manager (RPM) is a powerful command line-driven package management system used on our REd Hat systems that is capable of installing, uninstalling, verifying, querying and updating computer software packages. Our systems come with a list of pre-compiled binaries from the vendor or our development team.

Customizing packages is a task that most Linux administrators undertake on a daily basis. In order to properly install customized pre-compiled software (unsupported) on your server, or a customized, pre-compiled version of what we provided with the OS, you have a couple of options of how to proceed. Both of the options we suggest below will ensure that those customizations do not get overwritten by the updates that we release from time to time via up2date.

Option 1
Download the source RPM for the package you want to install, recompile it and install it, taking care to also recompile any other packages with dependencies on that RPM. Next, add the proper exclusions for updates to the file /etc/sysconfig/rhn/up2date so up2date will not automatically download and apply updates we release. This:

1. prevents updates from overwriting your custom work;
2. keeps packages rpm-based for easier dependency detection and resolution;
3. is the 'proper' way of updating packages on an rpm-based linux installation.

Here is an example of /etc/sysconfig/rhn/up2date with apache (httpd) excluded:
pkgSkipList=httpd*;mod_ssl*;

and here is the output from up2date:

[root@ns ~]#  up2date

Fetching Obsoletes list for channel: rhel-i386-es-3...

Fetching rpm headers...

Name                          Version                Rel    
----------------------------------------------------------

The following packages were marked to be skipped by your configuration:

Name                           Version                  Rel               Reason
-------------------------------------------------------------------------------

httpd                             2.0.46         57.ent.STOCKPkg   name/pattern

httpd-devel                    2.0.46         57.ent.STOCKPkg   name/pattern

mod_ssl                         2.0.46         57.ent.STOCKPkg   name/pattern

Option 2
Alternatively, you could uninstall the RPM package that the system came with first before recompiling the software, and do a source-based install. This will do two things:

1. Reveal dependencies by other components of the os on that package that will also need to be uninstalled and re-compiled against your source;
2. prevent future up2date releases from overwriting your customized re-compilation.

By not performing either of the two options referred to above, you run the risk of having your customizations overwritten by updates that PEER 1 releases via up2date. By working together we will ensure the security and integrity of your server.