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KVM Disk Image Management

Convert Disk Image Formats

1. With qemu installed, this works. In this example, converting from a VDI VirtualBox format to Qcow2. Note that that is -O (capital O) not -0 (zero)
   • qemu-img convert -f vdi -O qcow2 ubuntu.vdi ubuntu.qcow2

Mount Disk Image in Linux

This is might be specific to qcow2 image files.

DO NOT mount the disk image in read/write mode while the VM is running!

1. Install libguestfs-tools
   • apt install libguestfs-tools
2. Create a mount point:
   • mkdir /mnt/guestIMG
3. Mount it (replace device with anything to get a list of what devices are available):
   • guestmount -a /path/to/qcow2/image -m <device> /mnt/guestIMG
   • note that this does NOT require super user permissions if your user has full access to the mount point and image
   • use guestmount -a /path/to/qcow2/image -m <device> --ro /mnt/guestIMG to make it read only (which would allow you to mount while the VM is running)
4. Unmount it when finished:
   • guestmount /mnt/guestIMG
5. resource

Resize Qcow2 Disk Image

1. qemu-img resize diskImage.qcow2 +5G
   • resource
2. after that, launch the VM and resize partitions

Shrink Qcow2 Disk Image

1. virt-sparsify bloatedDiskImage.ext outputShrunkDiskImage.ext
   • this appears to support qcow2, vdi, and raw (img I think?)
   • Conjecture - I think if you have a qcow2 image you can use --in-place to avoid having to create a second image
   • more info
   • Alternatives
     • 1 look into virt-sparsify
     • 2 - less efficient, but more stable?
     • 3 - alt zeroing method
2. Be sure to test the resulting image before deleting the original

this document last modified: May 15 2018 01:00

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