Policies

Package management

Generally speaking, it is preferred to keep all install software under package management, i.e., RPM. Mostly because it makes software maintenance much easier. Old and obsolete files get removed during upgrades and/or uninstalls. You can verify administrative integrity easily (rpm -V). You can figure out where files come from (rpm -qf).

When building packages from source, it is thus considered a best practice to build an RPM package and install that, rather then using a simple make install. These days, many upstream authors provide the RPM .spec files needed in their source distribution. In other cases, one can find a third-party who provides a .spec or .srpm file. In these cases, buidling an RPM becomes almost trivial.

For Perl modules, see cpan2rpm, below.

Package repositories

Generally speaking, it is preferred to stick with the software the distribution provides, unless there are good reasons to use a third-party package. Sticking to a single source of software means security updates and system upgrades become hugely easier. There will, of course, be reasons to go outside the distribution.

Furthermore, when going outside the distribution, try looking in "big name" repositories first. For example, RPMForge provides a large number of independent packages. We even have the RPMForce repository configured for YUM on liberty; it just isn't enabled by default. By keeping the number of places we have to go to to get software to a minimum, we again make updates and upgrades easier.

Repository priorities

When a third-party repository is configured, use the yum-priorities plugin to configure the "stock" repositories to have a higher priority (lower number) than the third-party repo. This keeps the third-party repo from unexpectedly upgrading the distro beyond recognition. Make sure the plugin is installed and enabled (in /etc/yum/pluginconf.d/priorities.conf)!

Our convention for priority numbers is:

We skip numbers to allow fine-tuning as needed in the future.

Package kit storage

For packages which are downloaded manually (i.e., not via up2date or yum), the original package file (binary RPM, source tarball, whatever) should be stored under the /usr/local/adm/pkgs/ directory. This makes reinstalls easier, and reduces duplication of download.

Unmanaged installs

For software which is not under package management (e.g., installed via make install), the software should either be installed into the integrated /usr/local/ tree, or under a directory under /opt/. For example, if we had to build Apache from source, we whould end up with one of /usr/local/sbin/httpd or /opt/apache/bin/httpd for the main binary. As of this writing, a preference between the two has not been established. However, unmanaged software should not be installed under /usr/ (which is reserved for managed software).

Tools

rpm, yum, and up2date

The standard tool for package management on Red Hat-derived systems is rpm. For dependency management and package retrieval, Red Hat provided up2date, which works just fine on CentOS. The third-party yum tool is also provided with CentOS. Both up2date and yum are configured to pull from the same CentOS repository mirrors, and can be used interchangeably.

cpan2rpm

Installing Perl modules is frequently needed. A third-party tool called cpan2rpm is installed to make this much easier. In short, running cpan2rpm Foo::Bar will automatically download, build, and package that module from CPAN, resulting in RPM and SRPM files which can be installed on any RPM-enabled system.

Python setup.py bdist_rpm

There is a way to build RPM packages out of Python packages, provided the Python package includes the needed "setup.py", and possibly (depending on complexity of the package) a manifest. Download and unpack the Python source kit distribution, and then issue the command python setup.py bdist_rpm. That should result in a dist subdirectory containing RPM and SRPM files.

Examples

Using RPMForge

Subversion was, on one iteration of the system, upgraded to 1.2.1-0.1.2.el4.rf from RPMForge.

Since not everyone here is familiar with yum, here is how it was done:

1. I checked to see if there was a CentOS update that got missed somehow:
   yum list updates subversion
2. Nope. Okay, next was to check to see if RPMForge had something newer:
   yum --enablerepo=rpmforge list subversion
3. Yup, that found a newer version than what CentOS had -- the 1.2 Paul was looking for. Okay, so after checking with Paul (and making sure no one else was logged in), I ran the update:
   yum --enablerepo=rpmforge update subversion

And that was about it.