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[Xen-users] LVM partition resize pain...



Hi All-

Was hoping someone would know what's going on here....

I created a Xen VM on top of a LVM volume. The volume was like 530GB big. Within the volume sits the VM, with 5 partitions, one of them 500GB big (the other 4 file systems comprise the other 30GB). Each virtual disk partition exists as /dev/xvda1 - /dev/xvda5. /dev/xvda5 is the one with the 500GB file system on it.

I wanted to reduce the size of the filesystem on /dev/xvda5 from 500GB to 5GB. So I unmount /dev/xvda5 then run:

# resize2fs /dev/xvda5 5G

Works great. Next, I shut down the VM and reduce the size of my logical volume:

# lvreduce -v -L 40G /dev/vg0/xen1

So the volume is still larger than all the filesystems in it, such that I don't lose any data. The command worked successfully. Then I booted the VM and got errors on boot say something about "/dev/xvda: wanted 500000000 but was limited to 5000000" or something like that. But the VM booted even after the errors and appeared to work OK. So I:

# fdisk -l

Disk /dev/xvda: 32.2 GB, 32212254720 bytes
255 heads, 63 sectors/track, 3916 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

    Device Boot      Start         End      Blocks   Id  System
/dev/xvda1   *           1          13      104391   83  Linux
/dev/xvda2              14        1288    10241437+  83  Linux
/dev/xvda3 1289 2308 8193150 82 Linux swap / Solaris
/dev/xvda4            2309       67620   524618640    5  Extended
/dev/xvda5            2309       67620   524618608+  83  Linux

Notice it says that /dev/xvda is 32.2GB (which is correct), but /dev/xvda4-5 still think they are 500GB big! A 'df' shows that the filesystem is really only 5GB though, as expected. I tried some parted magic but parted can't do anything (even print the partition table!), I get errors like:

[root@template ~]# parted /dev/xvda
GNU Parted 1.8.1
Using /dev/xvda
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) print
Error: Can't have a partition outside the disk!
(parted)

and it won't let me make changes, etc. Is there something I missed? Wasn't the OS supposed to recognize the size change in /dev/xvda on boot? Or do I have to manually change the disk label or something? Is it just impossible to resize a VM's file system then change the volume the VM sits on to reflect the change?

Thanks so much for any ideas!

-erich


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