FAI Lab With VirtualBox (Part III)

11 November 2011

Note: This post is the third in a series of posts about setting up an FAI lab using VirtualBox. Here are part I and part II

In Part I of this series we set up a VirtualBox virtual machine to act as a DHCP/PXE server and configured a basic FAI nfsroot for other VMs to boot into. In Part II we configured FAI so that we could install Ubuntu onto PXE-booted virtual machines. In this part, I was going to tell you how to FAI a Redhat system, then see if we could make it easy to PXE boot into a “live” system for debugging, etc. Then I talked to a colleague who is more familiar with RPM-based distributions and he assured me that FAI was the wrong way to do it, and told me to use kickstart. After some basic research, I’m definitely inclined to agree. So instead of using FAI to bootstrap our Redhat VMS, I’m going to show you how to PXE-boot off our existing “faiserver” VM into a kickstart installation.

Kickstarting a Redhat install

By now you should be familiar with the VirtualBox commands to create a new VM configured to network boot. Refer to part II if you need a refresher . Create a VM (don’t forget to use the correct --ostype argument); I’m calling mine “redhat” for the purposes of this article. Add the MAC to /etc/ethers on “faiserver” and assign it an IP address in /etc/hosts. Use pkill -HUP dnsmasq to get dnsmasq to reload those files.

Now we need to set up our kickstart environment. You’ll need an ISO of the Redhat version you want to install. Create /srv/kickstart (or whatever path you want) and /srv/kickstart/iso. Mount the ISO (mount -oloop /srv/kickstart/rhel-server-5.4-x86_64-dvd.iso /srv/kickstart/iso, and you may want to add it to /etc/fstab) at /srv/kickstart/iso and add it to /etc/exports. Put your kickstart file in /srv/kickstart (more on getting the kickstart file later) and export that as well. I called mine /srv/kickstart/rhel5.4-x86_64.cfg. There are a few items we need to copy off of the ISO into the TFTP server directory. Copy /srv/kickstart/iso/images/pxeboot/vmlinuz to /srv/tftp/fai/vmlinuz-rhel5.4-x86_64 and /srv/kickstart/iso/images/pxeboot/initrd.img to /srv/tftp/fai/initrd.img-rhel5.4-x86_64. (We’re hijacking the “fai” sub-directory of the TFTP server, but that’s not really important.)

Next, we need to create a file in /srv/tftp/fai/pxelinux.cfg to tell the PXE-booting system which kernel, initrd, and kernel parameters to use. We don’t have the convenient fai-chboot command to generate this file for us in the case of Redhat (though you could use it to make a template if you’d like). The filename should be the IP address of the host you are booting, in hex. My “redhat” VM has the IP address - I could leave this as an exercise to the reader, but I’m always forgetting how to do this too, so:

  1. Remember, each component of the IP address is 2 hexadecimal digits.
  2. The first component is 192. printf '%x\n' 192 gives us c0.
  3. printf '%x\n' 168 gives us a8.
  4. 0 in hex is just 0, but each component is to digits, so: 00.
  5. Finally, 11 in hex is easy to remember - that’s just b. Again, two digits, so 0b.
  6. The filename is in all caps, so we are left with: C0A8000B as the filename we need to create, with the following contents.
default kickstarter

label kickstarter
kernel vmlinuz-rhel5.4-x86_64
append initrd=initrd.img-rhel5.4-x86_64 ip=dhcp autostep ks=nfs: method=nfs: text
  1. This line tells the boot loader to load the section labeled “kickstarter”.
  2. Blank.
  3. This is the label referred to by line #1.
  4. This is the name of the kernel we’re going to boot (which we copied from the RHEL ISO).
  5. These are the kernel parameters.
    • initrd=initrd.img-rhel5.4-x86_64 specifies the initrd we copied from the RHEL ISO.
    • ip=dhcp tells the kernel to use DHCP to configure the network interface.
    • autostep tells kickstart to run non-interactively.
    • ks=nfs: tells kickstart where to locate the kickstart file.
    • method=nfs: tells kickstart where to locate the RHEL installation tree (the ISO we mounted and exported).
    • text tells kickstart to run in text mode.

I dug these kernel parameters out of the Red Hat Enterprise Linux 5 Installation Guide; specifically section 31.10.

“Where did this kickstart file come from?” you are wondering. Well, the easiest way to get one is to run through the install process manually once. This will leave a kickstart configuration in /root/anaconda-ks.cfg. You can then tweak this file until you have a solid basic installation to work from. Here’s mine - the documentation is actually pretty good, and will help you modify the basic kickstart file to match your needs.

Now that we have a way to bootstrap multiple distributions, we’re in pretty good shape for our FAI lab. I’m going to take some time to implement what I’ve learned in production. Next time I write I’ll try to show you how to PXE boot into a “live” system for debugging, etc.