Red Hat Enterprise Linux and Virtual Machines
Friday, November 30th, 2007OMG, virtual machines are soooo hot right now. Good thing Red Hat has an over engineered solution to an already solved problem…
That’s not entirely true, I’m just being bitter that I can’t use Debian. Red Hat has a nice thing called Cobbler. It’s most useful when you have to install a whole bunch of systems and have one set of CDs and like, hate installing from CD. For example, copying text from it’s bawdy over-the-top “quick start guide”:
- yum install cobbler
- cobbler check
- /var/lib/cobbler/settings for ’server’ and ‘next-server’ addresses
- Mount the RHEL installer disk
- cobbler import –mirror=/media/dvd –name=RHEL
- cobbler sync
You’re done. Really.
So that’s true.
Then to make a new virtual machine, you have to set up some virtual bootstrap process like this:
Want to install a xen guest instead? No problem.
- yum install koan
- koan –virt –server=bootserver.example.com –profile=RHEL5-mount-xen-x86_64
Done.
And that’s where it’s over simplified, not “no problem” or “done”.
I was expecting the installer start installing after running this command. It doesn’t. You have to manually attach to the virtual console and run through some basic anaconda configuration by hand. I suppose I could edit the kickstart to remove these requirements but judging from the tone of the cobbler docs, this would be unecessary because cobbler makes it that simple. Anyhoo, I spent quite a while poking at cobbler and koan trying to figure out how to customize it to my liking.
First, create a LVM group named vg0 on a physical volume dedicated to housing virtual machine storage. I’m leaving this exercise to the reader. It’s well documented. Then deploy your virtual machine with some extra options:
- koan –server=localhost –virt –profile=RHEL5-mount-xen-x86_64 –virt-name=servername –virt-path=vg0 –virt-type=xenpv
- xm console servername
You will be dropped into the anaconda installer screen. For some reason it didn’t honor my network settings even after manually setting them. Everything else is automatic until it finishes installation and shuts down. Then you have to start the machine back up with $xm create -c servername and finish configuration.
So that’s the hard part. Everything else isn’t that much different than maintaining a real server. My gripes with cobbler are the author’s assumptions that it’s so simple. It’s not. If you are deploying a bunch of VMs, odds have it your configuration is complex. While the cobbler/koan framework accounts for this, it implies that it’s unnecessary. In reality, cobbler appears to be automating automation, in that it is using sensible defaults to generate a kickstart file and a xen guest configuration.
