[PLUG] boot from USB, run on RAID?

[Robert Citek]

On Tue, Jun 17, 2008 at 6:04 PM, Kurt Sussman <plug at merlot.com> wrote:
> And build a custom initrd with a linuxrc script that loads drivers,
> mounts the RAID device, and runs pivot_root.

OK.  If that's what you need to do for your Linux distro, then that's
what you need to do.  For me all I need to do is tell grub where the
kernel and initrd are.

If they are on the internal drive, then grub's root becomes (hd1,1)
(Linux happens to be on /dev/sda2 on my desktop):

title           Ubuntu, kernel on internal drive
root            (hd1,1)
kernel          /boot/vmlinuz-2.6.22-14-server root=/dev/sda2 ro quiet splash
initrd          /boot/initrd.img-2.6.22-14-server

If I copy the kernel and initrd to /boot/ on the USB drive, then
grub's root becomes (hd0,0):

title           Ubuntu, kernel on USB drive
root            (hd0,0)
kernel          /boot/vmlinuz-2.6.22-14-server root=/dev/sda2 ro quiet splash
initrd          /boot/initrd.img-2.6.22-14-server

What's key is that the root= parameter points to the root filesystem,
which may be the same as or different from where the kernel is.
Notice that it remained unchanged.

In both cases, I can unplug the USB drive once I get a login screen
(probably earlier).

Regards,
- Robert