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After installing updates on SLES/OES servers we have had issues where the server doesn't boot. The console comes to:

"No root device found; exiting to /bin/sh
sh: "

Usually the console is unresponsive.

This is because the kernel was upgraded and a new initrd was created but it was not created with EVMS support (for some reason, not sure why, wonder when Novell/Suse is going to fix this??).

Mostly copied from:
http://www.lotterer.net/blog/en/51-sles10-with-evms-missing-root-past-boot

# boot with the SLES10 AMD64/EMT64 CD1 or DVD. Use the correct arch, 32 or 64 bit.
The link says to use rescue mode of a SLES cd, but I like using RIPLinux 7.2. (the newer versions don't support evms). RIPLinux 7.2 has a smaller footprint so it boots faster.

# boot to rescue mode and enter "root" at the prompt. You will be at a command prompt.

#This isn't needed, but I left it just in case.
# sidenote: to access a CD/DVD at this point, use
# modprobe ide-cd; mkdir -p /mnt; mount /dev/hda /mnt

# probe EVMS information
echo "probe" | evms -s

# query devices
echo "q:d" | evms -s

# query volumes, this should display the name your root container
echo "q:v" | evms -s

#If you know your mount points, you won't really need to use the commands above.
# mount root (note the comma in the mount command after the "sys_lx")
This should be mounting your root files system.
echo "mount:/dev/evms/lvm2/system/sys_lx,/mnt" | evms -s

If you have /var as a separate partition you'll want to mount it also.
Ex:
mount /dev/evms/lvm2/system/var /mnt/var
#and if boot is separate: (it should be)
mount /dev/evms/sda1 /mnt/boot

# you should see your valuable data on the old root
ls -l /mnt/

# turn your old root into the current root
mount -t proc none /mnt/proc
mount -o bind /dev /mnt/dev
chroot /mnt /bin/bash
#you must choose the correct RIP kernel for your architecture.
#you may get an error here if you did not choose the correct arch

# create a new EVMS ramdisk
/sbin/mkinitrd -f evms

#exit chroot
exit
#dismount volumes
umount /mnt/boot
umount /mnt/var
umount /mnt

# shutdown properly and reboot
init 6
or reboot
#or press CTRL+ALT+DEL

Disclaimer: As with everything else at Cool Solutions, this content is definitely not supported by Novell (so don't even think of calling Support if you try something and it blows up).

It was contributed by a community member and is published "as is." It seems to have worked for at least one person, and might work for you. But please be sure to test, test, test before you do anything drastic with it.