Igor Clark

I just found myself in the situation of needing to install a load of software on a RHEL 4 box which had not had up2date set up. “Simple,” I thought, “it’s RPM-based, so just install yum and all will be well. yum’s nicer than up2date anyway, so”.

A cursory Google threw up this guide to doing just that, but I found that the list of RPMs provided was incomplete, possibly due to the age of the article. With the duplicates removed, package versions matched, and downloads sourced from the up-to-date CentOS and pbone, the set now installed without dependency problems, but left a non-functioning yum installation:

Setting up Install Process
Setting up repositories
not using ftp, http[s], or file for repos, skipping - Null is not a valid release or hasnt been released yet
Cannot find a valid baseurl for repo: update
Error: Cannot find a valid baseurl for repo: update

I hadn’t delved into yum’s config or repository setup much before, as on most non-RHEL rpm-based distributions it tends to work out of the box; I’d added other repositories, notably Dag Wieers’, but not looked at the format much. Imagine my delight on realising that now was my chance.

A first glance at the repository definition in /etc/yum.repos.d/CentOS-Base.repo suggested trying to use the baseurl entry which is commented out by default, rather than the mirrorlist. No joy, but it gave a pretty obvious clue:

http://mirror.centos.org/centos/Null/os/i386/repodata/repomd.xml: [Errno 14] HTTP Error 404: Not Found
Trying other mirror.
Cannot open/read repomd.xml file for repository: update
failure: repodata/repomd.xml: from update: [Errno 256] No more mirrors to try.
Error: failure: repodata/repomd.xml: from update: [Errno 256] No more mirrors to try.

Got it? That nasty Null is caused because the repository definition file uses a variable $releasever which, as man 5 yum.conf tells us, is taken from the currently installed version of the package named as distroverpkg in /etc/yum.conf - which by default is centos-release (presumably taken from the RHEL redhat-release convention). Thus the only step necessary to get it working was to install the centos-release package. The baseurl entry in the repository definition could be commented out again.

So here, for your edification, and as an »aide-memoire« for me, is my list of the packages required to get yum working correctly on RHEL4:

centos-release
centos-yumconf
python-elementtree
python-sqlite
python-urlgrabber
sqlite
yum
yum-metadata-parser

Joy.