This guide will explain how to increase the size of a disk in Xen. I used XenServer 7.2, XenCenter 7.2 and an old CentOS 6 VM.

  • If you wish to use the XenCenter GUI:

    • shutdown vm
    • increase hard disk from within XenCenter
    • boot

  • If you wish to use the XenServer command line:

    • Find the disk with xe vm-disk-list vm="myVM"
    • You can try to resize with the VM online: xe vdi-resize uuid=<UUID HERE> disk-size=50GiB online=true
    • If this does not work, your guest OS does not support online resizing. Shut down the VM and try again, without the online=true parameter.

  • Make sure to have a few free bytes (e.g. remove some logs)

  • sudo bash

  • Check that the disk is larger than the volumes with fdisk. Here /dev/xvda shows 53.7 GB, while /dev/mapper/vg_root-lv_root shows 11.3 GB

    • fdisk -l
Disk /dev/xvda: 53.7 GB, 53687091200 bytes
255 heads, 63 sectors/track, 6527 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0009e177

    Device Boot      Start         End      Blocks   Id  System
/dev/xvda1   *           1          64      512000   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/xvda2              64        1567    12069888   8e  Linux LVM

Disk /dev/mapper/vg_root-lv_swap: 1073 MB, 1073741824 bytes
255 heads, 63 sectors/track, 130 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000


Disk /dev/mapper/vg_root-lv_root: 11.3 GB, 11274289152 bytes
255 heads, 63 sectors/track, 1370 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

  • Now the dangerous part: we resize the partition of the disk.

  • Note: press [enter] after every single letter command.

    • fdisk /dev/xvda
      • If it shows the DOS-compatible mode warning:
        • c
        • u
      • Then change the partition table:
        • p
Disk /dev/xvda: 53.7 GB, 53687091200 bytes
255 heads, 63 sectors/track, 6527 cylinders, total 104857600 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0009e177

    Device Boot      Start         End      Blocks   Id  System
/dev/xvda1   *        2048     1026047      512000   83  Linux
/dev/xvda2         1026048    25165823    12069888   8e  Linux LVM
  • First delete partition 2 on xvda.
    • d
Partition number (1-4):
  • Select partition, 2 in our case.
    • 2
  • Now create a new partition which starts at the same cylinder, but extends to the whole new drive. You can normally use the default values.
    • n
    • p
    • 2
First sector (1026048-104857599, default 1026048):
  • Use default
    • [enter]
Using default value 1026048
Last sector, +sectors or +size{K,M,G} (1026048-104857599, default 104857599):
  • Use default
    • [enter]
Using default value 104857599

Command (m for help):
  • Then set the type to Linux LVM again.
    • t
Partition number (1-4):
  • Select partition, 2 in our case.
    • 2
Hex code (type L to list codes):
  • Set type to Linux LVM
    • 8e
Changed system type of partition 2 to 8e (Linux LVM)
  • Check the new partition:
    • p
Disk /dev/xvda: 53.7 GB, 53687091200 bytes
255 heads, 63 sectors/track, 6527 cylinders, total 104857600 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0009e177

    Device Boot      Start         End      Blocks   Id  System
/dev/xvda1   *        2048     1026047      512000   83  Linux
/dev/xvda2         1026048   104857599    51915776   8e  Linux LVM
  • If everything is correct, write changes to disk.
    • w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.

  • reboot and again make sure there are some bytes available

  • Now we can use the lvm tools to resize the logical volume.

    • lvm pvresize /dev/xvda2
 Physical volume "/dev/xvda2" changed
  1 physical volume(s) resized / 0 physical volume(s) not resized

  • Now we use lvextend to resize the disk, -r automatically runs resize2fs doing an online resize. -l +100%FREE extends the disk to the new fulle size.

    • lvm lvextend -r -l +100%FREE /dev/mapper/vg_root-lv_root
Size of logical volume vg_root/lv_root unchanged from 48.50 GiB (1552 extents).
Logical volume lv_root successfully resized
resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/mapper/vg_root-lv_root is mounted on /; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 4
Performing an on-line resize of /dev/mapper/vg_root-lv_root to 12713984 (4k) blocks.
The filesystem on /dev/mapper/vg_root-lv_root is now 12713984 blocks long.
  • Check the size of the local disk:
    • df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg_root-lv_root
                       48G   11G   36G  23% /
tmpfs                 936M     0  936M   0% /dev/shm
/dev/xvda1            477M   51M  401M  12% /boot

Profit.