Re: [Xen-users] how do I increase a LVM based xen domU?

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Thu, Sep 18, 2008 at 08:31:28AM +0200, Rudi Ahlers wrote:
> Hi all
> I know for many this is probably an easy answer, but I just can't figure it
> out.
> 
> How do I increase the size of a xen domU that's installed on a LVM
> partition?
> 
> >From what I can gather from Google searches, is that I need to use lvextend,
> but that doesn't seem enough.
> 
> So, what do I need todo to extend a 5GB LVM to say 8GB?
> 
> I have the following setup:
> 
> [root@saturn plugins]# lvscan
>   ACTIVE            '/dev/System/root' [10.00 GB] inherit
>   ACTIVE            '/dev/System/swap' [4.00 GB] inherit
>   ACTIVE            '/dev/System/pluto' [50.00 GB] inherit
>   ACTIVE            '/dev/System/home' [10.00 GB] inherit
>   ACTIVE            '/dev/System/data' [20.00 GB] inherit
>   ACTIVE            '/dev/System/andrew_vmswap' [1.00 GB] inherit
>   ACTIVE            '/dev/System/andrew_rootimg' [5.00 GB] inherit
>   ACTIVE            '/dev/System/keith_vmswap' [1.00 GB] inherit
>   ACTIVE            '/dev/System/keith_rootimg' [5.00 GB] inherit
>   ACTIVE            '/dev/System/12_vmswap' [1.00 GB] inherit
>   ACTIVE            '/dev/System/12_rootimg' [5.00 GB] inherit
>   ACTIVE   Original '/dev/System/wiseguy_rootimg' [10.00 GB] inherit
>   ACTIVE            '/dev/System/wiseguy' [5.00 GB] inherit
>   ACTIVE   Snapshot '/dev/System/oldcpanel' [32.00 MB] inherit
> 
> 
> 
> And I would like to increase the size of /dev/System/wiseguy
> 
> 
> 
> Inside the domU, I get the following:
> 
> 
> root@server [/scripts]# fdisk -l
> 
> Disk /dev/xvda: 5368 MB, 5368709120 bytes
> 255 heads, 63 sectors/track, 652 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         652     5132767+  83  Linux
> 
> 
> 
> 
> Can someone please tell me what commands I need to run to resize the LVM?
> 

I assume you have those LVM volumes in dom0. 

- lvextend the volume in dom0. 
- run "cat /proc/partitions" in domU. Check the size of xvda.
- shutdown domU and start it up again (to pick up the new size for xvda from 
the extended lvm volume) 
- run "cat /proc/partitions" in domU. Verify xvda is bigger now.
- create new partition to xvda, or resize existing partition (you can only grow 
the last partition easily)
- mkfs.ext3 the new partition or resize2fs the existing partition you just grew 
by editing the xvda partition table.

Xen doesn't support online resizing domU xvdX/vbd devices at the moment. 
So you need to restart domU to see the new/bigger size for xvdX devices. 

You could also run LVM in domU aswell.. to be able to resize any 
partition/volume in domU more easily.
In this case the procedure would be:

- lvextend the volume in dom0.
- run "cat /proc/partitions" in domU. Check the size of xvda.
- shutdown domU and start it up again (to pick up the new size for xvda from 
the extended lvm volume)
- run "cat /proc/partitions" in domU. Verify xvda is bigger now.
- resize/grow the LVM PV partition by editing partition table. Remember you can 
only grow last partition easily.
- reboot domU to make sure new partition sizes are picked up.
- run vgdisplay to check available/free space on your VG.
- run pvresize to resize the LVM PV.
- run vgdisplay to verify you have more free space in your VG now.
- lvextend any domU volume you want to.
- run resize2fs for the volume.

Another option is to have LVM PV directly on say xvdb, without any partition 
table..
Then you can skip the partition table editing steps.. just a simple reboot
will pick up the new size and you can pvextend immediately after.

-- Pasi

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