x-log - Archive

Thursday, 13. February 2014

Week 06

.: Moving a KVM guest to another machine

Properly shutdown the guest:
```
guest# poweroff
```
Create an LVM volume of the same size on the new machine:
```
newmachine# lvcreate -L 120G -n myguest myvolgroup
```

Copy the disk from the old machine over to the new one:

oldmachine# dd if=/dev/vg_foo/lv_bar | ssh newmachine dd of=/dev/volgroup/myguest

Wait for the transfer to complete (on a 100Mbit/s connection it took about 3.5 hours to transfer the 120GB).
Copy /etc/libvirt/qemu/myguest.xml from the old machine over to the new machine and adapt the LVM path for the disk.

Reload the libvirt configuration:

newmachine# /etc/init.d/libvirt-bin reload

.: Shrinking a LVM root partition

Boot from a helper system and get a root shell (I used the rescue mode of the Debian installer)
Check the filesystem of the partition to resize:
```
e2fsck -f /dev/vg_foo/lv_bar
```
Resize the filesystem (make it a bit smaller than the target size, to have a safety margin when resizing the logical volume):
```
resize2fs /dev/vg_foo/lv_bar 180G
```
Reduce size of the logical volume:
```
lvreduce -L 190G /dev/vg_foo/lv_bar
```
Grow the filesystem to the new size of the logical volume:
```
resize2fs /dev/vg_foo/lv_bar
```
For good measure run another filesystem check:
```
e2fsck -f /dev/vg_foo/lv_bar
```

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