Resizing a VM filesystem from Xen host
Resizing the disk and filesystem of a VM
I had to add more disk space to a Virtual Machine running under XenServer 6.0. In such situation I ususally do like this:
- create a snapshot (if possible, sometimes disk space makes it impossible)
- increase the virtual disk size using XenCenter (running from a Windows Virtual Machine…)
- boot Sysrescuecd and resize the filesystem using gparted
But this time, due to some known and unknown magic particular things (VT extensions disabled, ISO library avaialble on a remote NFS share with latency problems… I wasn’t able to boot sysrescuecd (nor other recent Live CD I tried), so one of my last option was to attach the VM’s virtual disk on the xen host (another VM could have been used too), here are the steps:
- Find xen host uuid
- Find VM uuid
- Find VM’s disk VDI uuid
- Create a new VBD for the xen host to plug the VDI in
- Stop the VM
- Plug the VBD
- Resize the partition and filesystem
- unplug and destroy the VBD
- Restart the VM
Hands-on
From the xenserver shell:
hostuuid=$(xe vm-list name-label='Control domain on host: xenserver-XXX' \
| awk '/uuid/ {print $5}')
xe vm-list uuid=$hostuuid
vmuuid=$(xe vm-list name-label=xxx.domain.tld | awk '/uuid/ {print $5}')
xe vm-list uuid=$vmuuid
xe vm-disk-list uuid=$vmuuid
vdiuuid=xxxx-xxxx-xxx-xxx-xxxx
xe vbd-list vdi-uuid=$vdiuuid
vbduuid=$(xe vbd-create device=0 vm-uuid=$hostuuid vdi-uuid=$vdiuuid \
bootable=false mode=RW type=Disk)
xe vbd-list vdi-uuid=$vdiuuid
xe vbd-plug uuid=$vbduuid
xe vbd-list vdi-uuid=$vdiuuid
Now the virtual disk of the VM is seen as a local device (/dev/xvda) on the xen host, it can be accessed using the standard fdisk, parted, mount tools.
At first I tried to use parted’s resize command but it didn’t work, so I add to delete and recreate the partition manually according to the cylinders. (be sure to save the layout of the partitions before messing with them…) (and using tmux is highly recommended for such tasks.)
parted /dev/xvda [86/818]
GNU Parted 1.8.1
Using /dev/xvda
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) unit s
(parted) print
Model: Xen Virtual Block Device (xvd)
Disk /dev/xvda: 83886079s
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Number Start End Size Type File system Flags
1 2048s 15988735s 15986688s primary ext3 boot
(parted) rm 1
(parted) mkpart
Partition type? primary/extended? primary
File system type? [ext2]? ext3
Start? 2048s
End? 83886078s
(parted) print
Model: Xen Virtual Block Device (xvd)
Disk /dev/xvda: 83886079s
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Number Start End Size Type File system Flags
1 2048s 83886078s 83884031s primary ext3
(parted) toggle 1 boot
(parted) print
Model: Xen Virtual Block Device (xvd)
Disk /dev/xvda: 83886079s
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Number Start End Size Type File system Flags
1 2048s 83886078s 83884031s primary ext3 boot
(parted) quit
Information: Don't forget to update /etc/fstab, if necessary.
resize2fs /dev/xvda1
resize2fs 1.39 (29-May-2006)
Resizing the filesystem on /dev/xvda1 to 10485503 (4k) blocks.
The filesystem on /dev/xvda1 is now 10485503 blocks long
fsck.ext3 -f /dev/xvda1
e2fsck 1.39 (29-May-2006)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/xvda1: 144207/2621440 files (3.3% non-contiguous), 1506575/10485503 blocks
xe vbd-unplug uuid=$vbduuid
xe vbd-destroy uuid=$vbduuid
xe vbd-list vdi-uuid=$vdiuuid
Done, the VM can now be restarted!