LVM resize sanity check

[brian]

Robert Locke wrote:
>
> Unmounting should only be necessary when "shrinking" a filesystem.  I
> thought you were growing /tmp....  But, now that you mention it, I
> didn't notice that you were unmounting and fscking /var before lvextend
> and resize2fs.
> 
> Generally growing should work with just lvextend and resize2fs, because
> you are only tacking things on to the end of the filesystem, not
> touching most of the existing data structures.
> 
> Shrinking is the more interesting challenge, because you are looking at
> the potential of "moving" data.  While this is handled just fine by
> resize2fs, it is "strongly" recommended to e2fsck beforehand to ensure
> you are starting from "stable structures".  So shrinking is normally:
> umount, e2fsck, resize2fs, lvreduce, and mount.  The danger is that
> lvreduce has no knowledge of the filesystem which resides on top of it,
> so is perfectly happy with shrinking into "live" structures.  That's why
> I was concerned with you using an "absolute" number for resize2fs and a
> relative number for lvreduce earlier.  To easy to slip up and lvreduce
> into the filesystem.
> 
> Good luck,
> 
> --Rob
> 

I've actually just rebooted after doing it from the rescue CD. Looks 
like everything went fine.

When trying from the GUI, I was only trying to increase the size of 
VolGroup03 (tmp) and not bothering with reducing /var as it showed that 
I had enough extra space to bring /tmp to 2GB. I thought I'd try that 
first. However, the application insisted on unmounting anyway. I'd think 
that that shouldn't be necessary, but whatever.

I understand about the reduction, and that it's important to reduce the 
filesystem first.

For posterity, here's what I just did from the rescue CD:

# umount /mnt/sysimage/var
# e2fsck -f /dev/VolGroup00/LogVol04
# resize2fs /dev/VolGroup00/LogVol04 13G
# lvreduce -L13g /dev/VolGroup00/LogVol04 <-- note the small g
# umount /mnt/sysimage/tmp
# e2fsck -f /dev/VolGroup00/LogVol03
# lvextend -L+6g /dev/VolGroup00/LogVol03
# resize2fs /dev/VolGroup00/LogVol03
# exit

Note that I didn't bother to remount because I was using the rescue CD.

That appears to have fixed things. Thanks for your help!