Right now, most of the testing is done using a qemu/kvm guest and
generating the initramfs on another box but the support is all present
to build for the "running" machine.  For the former, you can boot the guest
using qemu's -kernel and -initrd options.

dracut exists and will build an image.  It is command-line equivalent
to most mkinitrd implementations and should be pretty straight-forward
to use.

To use, just run dracut with an output file name and, optionally, a
kernel version (it defaults to using the current).   The appropriate
modules will be copied over and things should be good to go.  If you'd
like to customize the list of modules copied in, edit /etc/dracut.conf
and set
  dracutmodules="foo bar baz"

Note that dracut calls functional components in modules.d "modules"
while kernel modules are called "drivers".

Requirements:
* udev
* nfs module: nfs daemon and rpc helper
* iscsi: iscsi