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I have a bit of an unusual problem. I've installed lubuntu 12.10 AMD64 on my system, placing / and /boot on an SSD and the rest on a hard disk. Everything except /boot is encrypted. All was well until the SSD started producing I/O errors. It appears I'm going to have to return it for replacement, which means being without it for a few weeks.

As a substitute I copied everything from / and /boot onto an SD card, installed grub on it (grub-install /dev/sdf), and figured I could use the SD card as my boot disk until the replacement SSD arrives. However, Grub doesn't seem to agree - once the SSD is disconnected and the system powered on again, Grub boots from the SD card, but only says:

error: no such device: 5ab2e581-some-guid.
grub rescue>

I don't recognize that GUID it's complaining about - it's not in grub.cfg, grubenv, or any other text files I found in /boot, and sudo blkid doesn't show it.

Piecing together what information I could find about this prompt I came up with the following set of commands that seemed like they should be able to boot the kernel manually from here:

set root=(hd0,msdos1)/boot
set prefix=(hd0,msdos1)/boot/grub
insmod linux
linux (hd0,msdos1)/boot/vmlinuz-3.5.0-26-generic root=/dev/sde1 rootdelay=5

but the kernel doesn't seem to notice the SD card, and fails saying I need to provide an appropriate root= parameter and giving a list of available partitions - except the list is empty.

If, on the other hand, I do:

set root=(hd0,msdos1)/boot
set prefix=(hd0,msdos1)/boot/grub
insmod linux
linux (hd0,msdos1)/boot/vmlinuz-3.5.0-26-generic
initrd (hd0,msdos1)/boot/initrd.img-3.5.0-26-generic

it boots into an initrd image where I can see my SD card (on /dev/sde1, not /dev/sdf1, which is where I got sde1 in the above commands), but it doesn't appear there's any way to boot it from here either.

I don't know what I've missed here - what is this unknown GUID grub is looking for, and why isn't it able to find and boot the kernel on the SD card?

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How did you copy / and boot? At least one of the UUIDs have, apparently changed, and you'll need access to /etc/fstab in the / parttion to fix it. /etc/fstab contains the old UUIDs that Grub expects to find. You can use tune2fs -U to reset UUIDs. – mikewhatever Apr 9 '13 at 10:38
How did you format your sd card? Is it FAT or EXT4 or NFTS? – Misery Apr 9 '13 at 10:46
The card is formatted as ext4. I'll update the UUIDs in /etc/fstab and try again, though the one listed there isn't the 5ab2... grub complains about. I really have no idea where that one comes from. – Rena Apr 9 '13 at 12:16
Nope, updating /etc/fstab didn't help. – Rena Apr 9 '13 at 12:32
up vote 0 down vote accepted

Well, I did manage to get this working, in a way... I gave up trying to fix grub on the SD card and installed a brand new lubuntu install on it, then copied everything from the old system's root over it. The main issue was having to edit /etc/fstab and /etc/crypttab to deal with different GUIDs and device paths. (Since /dev/sda was removed, everything got shifted up a letter.) After doing that, it runs at least, though I suspect some things didn't mesh entirely nicely, as I get a lot of errors from .bashrc (or somewhere?) when opening a terminal now... but things seem to be working, anyway.

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