This section covers some questions that frequently come up in IRC, some of which are problems, and some of which are things about Cobbler that are not really problems, but are things folks just ask questions about frequently... all related to virtualization.
See also TroubleShooting for general items
There are two types of installer kernel/initrd pairs. There's a normal one (for all physical installations) and a Xen paravirt one. If you "cobbler import" an install tree (say from a DVD image) and get some "xen" distributions, these distributions will then not show up in your PXE menu -- just because Cobbler knows it's impossible to PXE boot them on physical hardware.
If you want to install virtual guests, read "man koan" for details and also Installing Virtual Guests
If you want to install a physical host, use the standard distribution, the one without "xen" in the name. Instead, in the "%packages" section of the kickstart, add the package named "kernel-xen".
This only applies for Xen, of course, if you are using KVM, it's simpler and there is only one installer kernel/initrd pair to worry about -- the main one.
In recent versions of Fedora, the Xen kernels have merged again, so this is not a problem.
If you use virt-type xenpv, make sure the profile you are installing uses a distro with "xen" in the name. These are the paravirtualized versions of the installer kernel/initrd pair.
Make sure your host arch matches your guest arch
If installing Xen and using virsh console or xm console, if you don't use --nogfx at one point the installer will appear to hang. Most likely it did not, it switched over to using VNC which you can view with virt-manager. If you would like to keep using the text console, use --nogfx instead. This does not apply to other virt types, only Xen.
There really aren't any KVM gotchas, other than making sure /dev/kvm is present (you need the right kernel module installed on the host) otherwise things will install with qemu and appear to be very slow.
See also Installing Virtual Guests
libvir: Xen error : Domain not found: xenUnifiedDomainLookupByUUID libvir: Xen error : Domain not found: xenUnifiedDomainLookupByName
If you see the above, it's not an error. These strange messages are perfectly normal and are coming from Xen as it's looking for an existing domain. It does not come from Cobbler/koan and your installation will not be affected. We agree they are confusing but they are not coming from Cobbler or Koan.
If you setup cobbler all correctly and you are trying to network book with PXE and you receive this error right after the VirtualBox POST:
FATAL: No bootable medium found! System halted.
Be sure to install to install the VirtualBox Extensions Pack to enable PXE boot support.