I had a similar problem after copying all files from the root partition
/dev/sda1 to another partition /dev/sdb1 and trying to tell grub to boot
from there now.
I digged into problem a little bit...
When i run `update-grub` it runs each of the files in `/etc/grub.d/`, my linux
copy (Ubuntu in this case) gets detected by `30_os-prober`. This will run
`/usr/bin/os-prober`. This works fine. In the `for OS in ${OSPROBED} ` loop it
goes into the linux) branch, but somehow sets the $LPARAMS variable wrong. This
is due to the sometimes-wrong output of `/usr/bin/linux-boot-prober`. In that
script, there is a loop `for test in /usr/lib/linux-boot-probes/mounted/*`,
which runs the file `40grub2` from there in my case. (I know that from the
debug output flooding syslog.) This script calls its `parse_grub_menu` function
with some parameters, and parses "$mpoint/boot/grub/grub.cfg", where $mpoint is
the mount point of /dev/sdb1. However, the grub.cfg in there contains the old
UUID of /dev/sda1, because it is just a binary copy and does not come from a
fresh install.
My plan A was to fix this, take the correct UUID from the device (here:
/dev/sdb1), corresponding to the mapping from /dev/disk/by-uuid/ and
post a patch. But the inner works of grub seem to complicated for me. I
lost motivation to do that.
Now that I know what the problem is, I took plan B, and chrooted into
/dev/sdb1, ran update-grub in there, and reboot. You only need to do that once,
afterwards the files are okay.
(...btw, for similar setups: you might want to have two different /etc/fstab on
each of the partitions.)
This is somewhat a workaround. But here it goes:
mount /dev/sdb1 /mnt/disk
mount -o bind /dev /mnt/disk/dev
mount -o bind /sys /mnt/disk/sys
mount -t proc /proc /mnt/disk/proc
cp /proc/mounts /mnt/disk/etc/mtab
chroot /mnt/disk /bin/bash
grub-install /dev/sdb
update-grub
exit
(Plan C would have been to update the grub.cfg with the correct UUID manually.)
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https://bugs.launchpad.net/bugs/508901
Title:
update-grub sets wrong root argument
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