From Fedora Project Wiki

Stateless Linux - NFS Loopback Root

See Stateless Linux HOWTO

This method is very similar to the method described in NFSRoot except that the root filesystem is available via an ext3 image on an NFS export. So, the NFS export is mounted, the image is associated with a loopback device and the loopback device is mounted as the root filesystem.

With mkinitrd >= 5.1.3-1 follow the instructions from NFSRoot except that instead of unpacking the image in nfs-export/, you place the image file there.

Also, mkinitrd is invoked differently:

$> chroot tmproot/ mkinitrd --loopdev \
--looppath terminal.img --loopfs nfs \
--rootfs ext3 -f /tmp/initrd.img 2.6.17-1.2510.fc6

With the mkinitrd in FC6 Test2 (5.1.2-1), you need to jump through a few extra hoops:

1. The NFS export must be mountable read/write 2. You need to pass --loopopts defaults to mkinitrd 3. You need to pass --rootdev /dev/loop0 to mkinitd 4. You need to add "loop nfs" to /etc/sysconfig/mkinitrd