well, for today’s monumental nightmare moment i decided to upgrade my disks on my FC6 server. bought three new ones to supplement the existing ones.
the end result of lots of planning and plotting and fiddling with LVM was that i had (i believe) succesfully made a complete copy of my root filesystem onto a new logical volume in a new volume group on a new software raid device.
so, modify the grub.conf to point to the new logical volume, modify the fstab (on the new volume, not the old one!) to refer to itself. bingo, right?
nope. boot can’t see the new volume even though it was right there a minute ago.
boot to single user mode using the old volume. the new volume is right back where it’s meant to be!
after a lot of worried checking i find that it’s just that LVM can’t find the new volume group because the new raid device doesn’t exist in /dev during boot.
a bit of googling later and i see we need to update the initrd file.
back into single user mode. a few experiments to check i’ve understood things right and then (after taking a backup of the original file):
mkinitrd –fstab=/mnt/newroot/etc/fstab -f /boot/initrd-`uname -r`.img `uname -r`
more checks to see that the only difference between the two is the addition of the new raid device.
reboot. bingo. now i’m pleased to report:
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/WideVG-WideLV 1.2T 397G 691G 37% /