Howto extend a KVM virtual disk, using lvm, with larger disk space

Prerequisites:
An installed KVM Ubuntu 10.04 guest with regular disk using LVM (lvm makes the resize operation a bit more tricky).
In this example the original disk was 20 GB and I want to extend it with 20GB more.

1. Stop guest


2. Extend imagefile med zeroes to desired size
   - create addon space with the size you want to extend disk with
   sudo qemu-img create -f raw addon.raw 20G
   - make backup of the original disk
   mv ubuntu-dev.img ubuntu-dev.img.save
   - concatenate the extra space on top of the old image
   cat ubuntu-dev.img.save addon.raw >> ubuntu-dev.img
   


3. Start guest with gparted live iso
   Partitions might look like:
   

   Number  Start   End     Size    Type      File system  Flags
   1      1049kB  256MB   255MB   primary   ext2         boot
   2      257MB   20.5GB  20.3GB  extended
   5      257MB   20.5GB  20.3GB  logical                lvm
   

   
   - extend physical partition (2) with gparted (easiest) to fill upp the entire (new) disk
   


4. Reboot into guest
   - Remove the logical partition (lvm)
   - Create a new logic partition, with exact same start but new ending
   rm 5; mkpart logical ext2 0 4000; set 5 lvm on
   


5. Resize the lvm physical volume (use pvdisplay to find out the device /dev/vda5)
   - pvresize /dev/vda5
   


6. Resize the lvm locial volume
   - lvresize -L+4309 /dev/www/root
   repeat the above until you fill up the entire free space, use pvdisplay and lvdisplay to see the free size
   


7. fsck the filesystem, the filesystem name is visible when you do lvdisplay
   - fsck -n /dev/www/root
   


8. Resize the filesystem to fill up the space
   - resize2fs /dev/www/root