Resize disks
1. Resizing guest disk
General considerations
When you resize the disk of a VM, to avoid confusion and disasters think the process like adding or removing a disk platter.
If you enlarge the hard disk, once you have added the disk plate, your partition table and file system knows nothing about the new size, so you have to act inside the VM to fix it.
If you reduce (shrink) the hard disk, of course removing the last disk plate will probably destroy your file system and remove the data in it! So in this case is paramount to act in the VM in advance, reducing the file system and the partition size. SystemRescueCD comes very handy for it, just add its iso as cdrom of your VM and set boot priority to CD-ROM.
Another page (deleted) with overlapping content was Resizing disks | Archive
qm command
You can resize your disks online or offline with command line:
qm resize <vmid> <disk> <size>
exemple: to add 5G to your virtio0 disk on vmid100:
qm resize 100 virtio0 +5G
For virtio disks:
Linux should see the new size online without reboot with kernel >= 3.6
Windows should see the new size online without reboot with last virtio drivers.
for virtio-iscsi disk:
Linux should see the new size online without reboot with kernel >= 3.7
Windows should see the new size online without reboot with last virtio drivers.
2. Enlarge the partition(s) in the virtual disk
Depending on the installed guest there is several diffent ways to resize the partions
Offline for all guests
Use gparted or similar tool (recommended)
In gparted and possibly most other tools, LVM and Windows dynamic disc is not supported
Boot the virtual machine with gparted or similar tool, enlarge the partion and optionally the file system. With som linux clients you often need to enlarge the extended partion, move the swappartion, shrink the extended partion and enlarge the root partion. (or simple delete the swap and partion andre create it again - but remember to activwate the swap agin (last step).
Gparted have some warnings about some specific operations not well supported with windows guest - outside the scope of this document but read the warnings in gparted.
Online for Windows Guests
- Guest is Windows 7, Windows Vista or Windows Server 2008
- logon as administrator and extend the disk and filesystem (Using Disk manager)
- For more info www.petri.co.il/extend-disk-partition-vista-windows-server-2008.htm
Online for Linux Guests
Here we will enlarge a LVM PV partition, but the procedure is the same for every kind of partitions. Note that the partition you want to enlarge should be at the end of the disk. If you want to enlarge a partition which is anywhere on the dis, use the offline methode.
- Check that the kernel has detected the change of the hard drive size
(here we use VirtIO so the hard drive is named vda)
dmesg | grep vda [ 3982.979046] vda: detected capacity change from 34359738368 to 171798691840
- Print the current partition table
fdisk -l /dev/vda | grep ^/dev GPT PMBR size mismatch (67108863 != 335544319) will be corrected by w(rite). /dev/vda1 34 2047 2014 1007K BIOS boot /dev/vda2 2048 262143 260096 127M EFI System /dev/vda3 262144 67108830 66846687 31.9G Linux LVM
- Resize the partition 3 (LVM PV) to occupy the whole remaining space of the hard drive)
parted /dev/vda (parted) print Warning: Not all of the space available to /dev/vda appears to be used, you can fix the GPT to use all of the space (an extra 268435456 blocks) or continue with the current setting? Fix/Ignore? F
(parted) resizepart 3 100% (parted) quit
- Check the new partition table
fdisk -l /dev/vda | grep ^/dev /dev/vda1 34 2047 2014 1007K BIOS boot /dev/vda2 2048 262143 260096 127M EFI System /dev/vda3 262144 335544286 335282143 159.9G Linux LVM
3. Enlarge the filesystem(s) in the partitions on the virtual disk
If you did not resize the filesystem in step 2
Online for Linux guests with LVM
Enlarge the physical volume to occupy the whole available space in the partition:
pvresize /dev/vda3
Enlarge the logical volume and the filesystem (the file system can be mounted, works with ext4 and xfs)
lvresize -L+1G --resizefs /dev/xxxx/root #This command will increase the partition up by 1GB -- not too helpful in most cases.
lvresize --extents 100%FREE --resizefs /dev/xxxx/root #Use all the remaining space on the volume group
Online for Linux guests without LVM
Enlarge the filesystem (in this case root is on vda1)
resize2fs /dev/vda1