[linux-lvm] successes & resizing

[Andreas Dilger]

Todd Underwood writes:
> i have a separate question about ext2 resizing on a separate system:  when
> i try to resize the root (using the ext2online resize patch to 2.4.3) i
> get:
> 
> Filesystem           1k-blocks      Used Available Use% Mounted on
> /dev/rootvg/root        495844    250577    219667  54% /
> /dev/rootvg/usr        2590504   1444748   1014072  59% /usr
> /dev/rootvg/home       1032088        20    979640   1% /home
> /dev/rootvg/var         495844    105794    364450  23% /var
> /dev/hda1               101089      6029     89841   7% /boot
> bash-2.04# e2fsadm -L +200M / 
> e2fsadm -- invalid logical volume name "/dev/root"

That is because in /proc/mounts, "/" is pointing to "/dev/root".  Sorry,
not much I can do about that - you need to specify the real device name
for root.

> bash-2.04# e2fsadm -L +200M /dev/rootvg/root 
> lvextend -- extending logical volume "/dev/rootvg/root" to 700 MB
> lvextend -- doing automatic backup of volume group "rootvg"
> lvextend -- logical volume "/dev/rootvg/root" successfully extended
> 
> ext2online v1.1.17 - 2001/03/18 for EXT2FS 0.5b
> new filesystem size 716800
> ext2online: group 0, block 4 not reserved
> 
> ext2online: unable to resize /dev/rootvg/root past 524288 blocks

Yes, please see ext2prepare(8) or ext2online(8), starting with the
paragraph "Because of the original design of the ext2 filesystem...
there are certain limitations to the amount of resizing that can be
done online..."  Clearly, you have a 1kB block filesystem for root,
because it started life at (just) less than 512MB in size.  You
could still online resize up to the 512MB limit without any other action.

To increase the filesystem size past 512MB, you need to (unfortunately)
boot from a rescue floppy which supports LVM so you can play with the
unmounted root filesystem (you may be able to simply change the LVM
initrd to go to a shell instead of booting the system... maybe that should
be an option for lvmcreate_initrd?).

Use ext2resize to resize the root filesystem to fill the current LV
(just run it with no size parameter will do the trick).

ALSO, run ext2prepare on the filesystem to prepare it for some nice
large size like 8GB (or whatever) so that the next time you need to do
online resizing of that filesystem you can do so (up to 8GB at least).
Don't make it _too_ large on a 1kB filesystem, as it starts sucking up
space at an increasing rate.

You should do this on your other filesystems as well, while you are there,
so that you don't run into the problem again later (for non-root fs it is
easier to fix, but still is a hassle if you can't unmount the fs).

For 4kB block filesystems, you may as well prepare them for 256GB or
whatever your max LV size is, it only costs a couple of kB in filesystem
space (ok, maybe 1MB or so, depending on the current filesystem size).
Use "dumpe2fs -h <dev>" to see the block size of the filesystems.

Cheers, Andreas
-- 
Andreas Dilger  \ "If a man ate a pound of pasta and a pound of antipasto,
                 \  would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/               -- Dogbert