Re: Re: [Xen-users] how to expand disk inside of domU?

[Matej Zary <zary@xxxxxxxxx>]

On Mon, 2010-04-26 at 15:36 -0500, Dan Waterloo wrote:
> i'm trying to find a way to expand a selected partition in my DomU...
> 
> when in a console in the domU, here are the disks available:
> 
> [root@localhost ~]# df -h
> Filesystem            Size  Used Avail Use% Mounted on
> /dev/mapper/VolGroup00-LogVol00
>                        13G  3.5G  8.1G  30% /
> /dev/xvda1             99M   21M   74M  22% /boot
> tmpfs                 257M     0  257M   0% /dev/shm
> 
> I'd like to expand the /dev/mapper/VolGroup00-LogVol00 disk to 25G
> 
> The domU is based on an image file, 'webs.img' that resides on a disk
> in the Dom0.
> In the dom0, I add space to the webs.img file with the following
> command:
> dd if=/dev/zero bs=1024k count=12288 >> webs.img
> 
> then, when i create the webs domu, i.e. xm create webs;
> it starts, and the new space shows up as "unintialized' space  
> in the domu. (I see this using vnc to reach the desktop, and 
> open the LVM tool to see the new space). 
> 
> The problem that I'm having is to 'attach' the unintialized space in the 
> domU to the /dev/mapper/VolGroup00-LogVol00 disk, and then to expand the 
> LogVol00 disk to take advantage of the space.
> 
> I'm running Centos5 on the dom0, and in the domU. Xen is version 3.
> 
> Any suggestions? if so, can you please be explicit as to _where_ to run the 
> various 
> commands, in the Dom0 or DomU? At this point, I'm pretty confused about 
> what to do where....
> 
> Thanks!
> 

So to sum it up - your DomU hdd is file based. This virtual disk is
"LVMed" in the DomU. You resized the virtual disk in the Dom0 and now
want to utilize this space into the domu using the LVM.

My guess is, you need to allocate the non-utilized new space to the main
LVM volume group. This volume group is made of actual physical volumes.
So this point me to pvresize, which can be used to extend existing
physical volume after extending the partition via fdisk. 

LVMs inside DomU can be pain in the *** sometimes, but it should be just
few more commands. 

Rough walk-thru (smaller steps are missing - man and google are good
friends):

0. back up your data
01. back up your data
02. well, do it, really!
1. shut down DomU
2. mount the virtual disk img file in the Dom0
3. expand the partition with fdisk
4. expand the physical volume with pvresize
5. expand the filesystem with apropriate command for your filesystem
(e.g. resize2fs) 

another solution could be using liveCD with some linux distribution with
LVM tools and boot it from virtual cdrom (iso image) in hvm VM setting
and do these steps "inside" the DomU. 


Someone correct me please if this is dumb solution. :)

Regards

matej

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