Sysadmin/Add resources to a VM

Hot-adding a virtio volume to a running VM

virsh vol-create-as housetree jita-srv 20G
virsh attach-disk  jita /dev/housetree/jita-srv vdb

Adding memory to a VM

Shutdown the VM

sudo virsh shutdown "name_of_vm"

Edit the configuration of the VM

sudo virsh edit "name_of_vm"

...
  <memory>XXXXXX</memory>    <--- XXXXXX is (number of gigabytes of memory * 1024 * 1024)
  <currentMemory>XXXXXX</currentMemory>    <--- XXXXXX Should be the same as the previous line

Start the VM

sudo virsh start "name_of_vm"

Extending a raw disk image

This procedure applies to full-disk images containing an MBR partition table.

• • NOTE: Any VM using this disk must be shut down beforehand, or you'll corrupt the filesystem!**

First, append some space at the end of the disk:

dd if=/dev/zero bs=1M count=$((1024-256)) >>example-boot.img

Then extend the partition to fill the entire disk:

parted example-boot.img

(parted) resizepart 1
End?  [267MB]? -1

(parted) p
Model:  (file)
Disk /var/lib/libvirt/images/boot/example-boot.img: 1074MB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags: 

Number  Start   End     Size    Type     File system  Flags
 1      1049kB  1073MB  1072MB  primary  ext4         boot

(parted) quit

Now create device nodes for the new partition table:

# kpartx -av lightwave-boot-new.img
add map loop7p1 (253:4): 0 2093152 linear 7:7 2048 

Grow the filesystem inside the partition (resize2fs requires an fsck beforehand):

# e2fsck -f /dev/mapper/loop7p1
# resize2fs /dev/mapper/loop7p1

Now loopback-mount your grown up filesystem to check if it's healthy:

# mount /dev/mapper/loop7p1 /mnt
# df -h /mnt
Filesystem           Size  Used Avail Use% Mounted on
/dev/mapper/loop7p1  986M  112M  820M  12% /mnt

Don't forget to unmount the filesystem and undefine the loopback devices!

umount /mnt
kpartx -d lightwave-boot-new.img

Et voilà!

Extending a QCOW disk file

Create a file containing the amount of space you want to add to the VM

sudo qemu-img create -f raw additional.raw <size>

Shutdown the VM ----- DO NOT SKIP THIS STEP. YOU WILL CORRUPT THE VM IF YOU DO THIS WHILE IT IS RUNNING

sudo virsh shutdown "name_of_vm"

Convert the VM to raw if needed

sudo qemu-img convert -f "name_of_vm".qcow2 -O raw "name_of_vm".raw

Add the additional space to the VM

sudo cat additional.raw >> "name_of_vm".raw