Hope I have the right person;  you may be interested in this.

I boot a CD using initrd; the RAMDISK uses devfs within the linuxrc script
to pivot_root/chroot as in the documentation.  In the documentation it
is suggested that root=/dev/rd/0  is used, if using devfs.

A boot using root=/dev/ram0 works fine, root=/dev/rd/0 shows a bug
in init/do_mounts.c, in void prepare_namespace(void)

The test:
if (initrd_load() && ROOT_DEV != MKDEV(RAMDISK_MAJOR, 0))
is true, and handle_initrd() is wrongly called.  This is a bug, (I assume
that this code is to relinquish the original boot).  The call that is used
is at the end of main.c where linuxrc is called instead of /sbin/init.

This is because rd/0 is not in root_dev_names; a patch is attached to fix
this.

Strangly enough, it still boots, despite linuxrc being called twice :-)

An alternative would be to change the documentation of initrd, so
that only root=/dev/ram0 is mentioned, despite using devfs.

Chris Lingard