The main feature of koan is contact the cobbler server, learn about a configuration from Cobbler, and make that virtualized installation happen. One other feature is [KoanDoesReinstall reinstallation of existing systems] but perhaps the more important one is how to do virtualized installs.
Koan is its own seperate tool, a seperate package from cobbler, that is designed for use with a remote cobbler server. (The same folks that work on cobbler work on koan and it's available from the same repositories)
yum install koan
It is a very small tool and generally does not always need to be updated when cobbler is updated, but keeping koan updated ensures you have all the latest features available. In general, the major release numbers of Cobbler and koan should match, but it's not so important if the minor release numbers don't match.
koan --server=cobbler.example.org --virt --profile=foo
koan --server=cobbler.example.org --virt --system=foo
Koan is designed to install things as set up in cobbler to ensure installs are consistent and repeatable.
Often though, users of koan may not be cobbler server administrators or may want to install a VM on a test system -- so they'll want to override some things as stored in cobbler. Koan allows an extensive system of overrides to tweak what Cobbler tells us about how a particular cobbler profile should be installed.
--virt-name name of virtual machine to create testmachine --virt-type forces usage of qemu/xen/vmware qemu --virt-bridge name of bridge device virbr0 --virt-path overwrite this disk partition /dev/sda4 --virt-path use this directory /opt/myimages --virt-path use this existing LVM volume VolGroup00 --no-gfx do not use VNC graphics (Xen only) (does not take options)
Nearly all of these variables can also be defined and centrally managed by the Cobbler server and are also described in the cobbler manpage in depth.