Category: cobbler

If you have not figured it out, I am a strong proponent and user of cobbler and kickstart installs. It is rare these days that I build a machine in what one might call a “hands-on” mode, whether using a Live DVD/USB flash drive, network install, or any other media. Indeed, I am even for the RHEL 8 beta install I have planned in the next 48 hours going to use cobbler and a kickstart install, where I will pull the trigger and come back in an hour or so to find everything installed and updated just the way I would a RHEL/CentOS 7 install, or most any other install I would expect to do. This is because when I was working at CompuServe, Bell Labs Messaging and later a network switch manufacturer, not only was I providing means for engineers, operators and folks on the factory floor of the latter to install the OS with minimal knowledge and effort, in my daily tasks, I needed to be able to do the same. And so, anything beyond perhaps a couple of quick commands and perhaps turning on the hardware was inefficient and “too much” in my professional opinion.

I will admit, there have been times this has not been easy… a new OS version which is not yet recognized by cobbler may take some time to be officially recognized by a released version is the most common. But over the past 24 hours, I found a new issue, for which I am going to start a discussion on the cobbler developer mailing list (which I will need to rejoin). The problem is that while cobbler allows you to specify a list of software repositories to use during your install, the mechanism used in placing those into the kickstart file sent to the machine being installed is an oddball in how it has been done which has become not only dated, but outright broken.

Cobbler has the ability to use templates and snippets to produce things like the kickstart file, or the various files it produces for maintaining the DHCP and DNS server. What is the difference between templates and snippets?? Personally, I would say that there is none…zilch, nada, nichts, rien, ничего, 別. Mathematically, if we have S represent what you can do with snippets and T represent that for templates, I would express it as S ⊖ T = Ø. I think the only “difference” is that templates are the term used for the top level snippet. But for the repository info used in the kickstart file, along with the similar information used during the configuration step, these are done by something else entirely. For these, cobbler uses a legacy mechanism called stanza’s, which go clear back to at least some 1.x version from the days when Michael DeHaan was maintaining it (which was when I first started using it, though I remember using the 0.x releases with x no higher than 4). The stanzas are actually produced by functions in the code itself, and not able to be changed without changing the code itself. As of right now, there appear to be only two such stanzas remaining: $yum_repo_stanza and $yum_config_stanza. And in a kickstart template, it might look something like this:

...
#
# Add in any cobbler repo definitions
#
$yum_repo_stanza

#
# System timezone
#
timezone --utc America/New_York
...

But, as I said, there was an issue with this, since it only provided the repo kickstart command with the name and URL, while both cobbler and kickstart have other information associated with them, such as what cobbler and the repo definitions themselves refer to as “priority”, but which the kickstart repo command calls more correctly “cost”. Why “cost” instead of “priority”? Because everywhere, it talks about how the repository with the lowest value is the one used, while “priority” would pick the one with the higher value. To fix this, I created snippets/yum-repos, which looks like this:

# My custom repo stanza
#for repo in $repo_data
repo --name=$repo['name'] --baseurl=$repo['mirror'] --cost=$repo['priority']
#end for

This changes the usage to this:

...
#
# Add in any cobbler repo definitions
#
$SNIPPET('yum-repos')

#
# System timezone
#
timezone --utc America/New_York
...

The result renders to this:

# Add in any cobbler repo definitions
# My custom repo stanza
repo --name=centos7-x86_64-local-secure --baseurl=http://mirror.ka8zrt.com/local-secure/centos/7/x86_64/ --cost=90
repo --name=centos7-x86_64-local --baseurl=http://mirror.ka8zrt.com/local/centos/7/x86_64/ --cost=90
repo --name=centos7-x86_64-extras --baseurl=http://mirror.ka8zrt.com/centos/7/extras/x86_64/ --cost=99
repo --name=centos7-x86_64 --baseurl=http://mirror.ka8zrt.com/centos/7/os/x86_64/ --cost=99

# System timezone
timezone --utc America/New_York

And so, with this, I can now do an installation where I create a local replacement for a package and have it used instead of the original, which in this case is a revised version of the setup-2.8.71-10.el7.noarch package, where I need only change the el7 to my ka8zrt-el7 when I generate the package. And when all is said and done, and the install the rpm -q -i command will still show something like the following…

Name        : setup
Version     : 2.8.71
Release     : 10.ka8zrt.el7
Architecture: noarch
Install Date: (not installed)
Group       : System Environment/Base
Size        : 697090
License     : Public Domain
Signature   : (none)
Source RPM  : setup-2.8.71-10.ka8zrt.el7.src.rpm
Build Date  : Fri 28 Dec 2018 06:23:12 AM EST
Build Host  : builds.home.ka8zrt.com
Relocations : (not relocatable)
URL         : https://pagure.io/setup/
Summary     : A set of system configuration and setup files
Description :
The setup package contains a set of important system configuration and
setup files, such as passwd, group, and profile.

So, having built the new version of the setup package (as you might have guessed from the output above), and made the update to my kickstart template, I have done the following command ¹

norway# koan --system=loki --virt --force-path

and when I wake back up, we shall see how this test install has worked out.

¹Bonus geek points to anyone who gets the references…