I want to backup kvm virtual machines and copy machine's images another path or usb disk? How to copy " qemu raw images"?

  • Do you use libvirt-based solutions like virt-manager or do you call kvm directly? – jofel Mar 12 '12 at 8:50
  • Do you want to backup a copy while the virtual machine is running or can you shutdown the VM for the backup? – jofel Mar 12 '12 at 8:52
  • I dont use libvirt or virt-manager and I can shutdown vm for the backup.Thanks. – psp mid Mar 12 '12 at 9:02

Copy kvm virtual machines is not complicated: First, you need to shutdown the virtual machine, then you need to find the disk image where the virtual machine is stored and finally copy it to another place (cp /path/to/disk_image /new_path/).

If the virtual machine is stored on its own partition, use dd if=/dev/PARTITION of=/path/to/backup/backup.img bs=1M or use ddrescue /dev/PARTITION /path/to/backup/backup.img.

The virtual machine images could be stored in different formats. Usually, the qcow2-format is used. To get the raw format, you can use qemu-img convert.

  • Note: you don't need to shutdown, you can suspend it, do the copy and resume it. That's what proxmox do, for instance. – Coren Mar 12 '12 at 10:12
  • I made it(shutdown and cp /path/to/disk_image /new_path/) already.But the file sizes are different.Why different? – psp mid Mar 12 '12 at 12:50
  • How did you check the file sizes? BTW, there are also checksum programs like sha1sum or md5sum. – jofel Mar 12 '12 at 12:56
  • orginal image : du -h ==>> 15G clone file: du -h ==>> 9,6G.I didn't check md5sum or sha1sum . – psp mid Mar 12 '12 at 13:06
  • du returns the used space on the file system. For sparse files this is different from the (real) file size. See en.wikipedia.org/wiki/Sparse_file for more information. – jofel Mar 12 '12 at 13:13

cp is enough for most files. If you prefer to use qemu's utilities, you can qemu-img convert with input and output formats both being raw

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