Automating Yum Setup

Recently, as part of my employer's "employee development" programs, I took Red Hat's RH255 class so that I could prep for getting my RHCSA and RHCE (my opinions on the experience are grist for another post - and I don't know, yet, whether that post should be in this blog or one of my personal blogs). The RH255 class I took was based on RHEL 6. In the US, they moved to training based on RHEL 6.0 about six months ago. One of the interesting things (I thought) my instructor said was that RHEL 6.0 included a function that tried to automatically configure `yum` to take mounted CDROMs and ISOs and treat them as installation repositories.

I may have misheard or misinterpreted what he said. It may also be a case that, since my instructor is in the RHEL 6.1 beta program, he was referring to a feature in RHEL 6.1 and not RHEL 6.0. Whatever the case may be, popping an RHEL 6.0 DVD (or ISO) into and RHEL 6.0 machine does not (yet) cause that DVD to be automatically included in `yum`'s repository search. Fortunately, the RHEL 6.x media has been set up (prior RHELs may also have been, it's just been so long since I've built an RHEL 5 system from other than an automated-build system) so that it's easy enough to automatically set up the DVD or ISO for inclusion in `yum`'s seaches. All of the yum repository is already on the media. So, you needn't muck about with doing the createrepo stuff (and the time that running createrepo against a multi-gigabyte DVD can take). Below is the script I wrote to take this already-present data and make it available to `yum`:

#!/bin/sh

MNTDIR=${1:-UNDEF}

# Make sure we passed a location to check

if [ ${MNTDIR} == "UNDEF" ]

then

   echo "Usage: $0 <ISO Mount Location>"

   exit

fi

# Make sure it's actually a directory

if [ ! -d ${MNTDIR} ]

then

   echo "No such directory"

   exit

fi

#ID directories containing repository data

REPODIRS=$(find ${MNTDIR} -type d -name repodata)

if [ "${REPODIRS}" == "" ]

then

   echo "No repository data found"

   exit

fi

for DIR in ${REPODIRS}

to

   DIRNAME=$(echo ${DIR} | sed -e 's#'${MNTDIR}'/##' -e 's#/repodata##')

   BASEURL=$(dirname ${DIR})

   echo "[${DIRNAME}]"

   echo "baseurl=${BASEURL}"

   echo "enabled=1"

   echo

done

The above script takes a directory location (presumably where you mounted your DVD or ISO) and produces yum repository configuration output. I opted to have it output as a capturable stream rather than as a file. That way, I'd have to option of either capturing to a temp location or  directly into /etc/yum.repos.d. Doing so gave more flexibility in what to name a file (so that I didn't clobber any existing files). Granted, I could have parameterized the name and location of the output file, but chose not to. If you want to use the above and would rather have the output go directly to an output file in /etc/yum.repos.d (or elsewhere), it's a trivial modification to the above. Have at it.

At any rate, once you run the above and take the resultant output and move it into a file in /etc/yum.repos.d, subsequent invocations of the `yum` command should now include your DVD or ISO. If it fails to do so (or errors result) it's probably because the new .repo file contains section IDs that collide with exiting ones. Just edit your new file to eliminate any collisions.

While I've done some basic error-checking in the file (specifically: ensuring the user passed a location and that the location is a valid directory), I didn't write it to gracefully handle repository directories that have spaces in their path-names. It's also fairly trivial to fix the script to accommodate it. However, it's probably even easier to just make sure you don't mount your DVD or ISO with spaces in the path-names. I'm lazy, so, I'm choosing the latter option and avoiding the coding exercise. If you find you need to have spaces in your path-names and want to use my script, feel free to make the necessary modifications to accommodate your use of space-containing path names.