Cloning a computer

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Cloning a computer means you have one computer and want to copy the complete harddisk to another. This can mean different things and can have different reasons.


  • You want to have a backup of your computer. In this case it is enough to copy every file from hard disk A to hard disk B.
  • You want to virtualize your computer. In this case you will have to dump every byte from your source (physical) to your target (virtual) computer.
  • You are an administrator and want to deploy many computers with the same configuration.


You can either clone byte-by-byte or file-by-file. The advantages are:

  • cloning byte-by-byte will clone the boot sector. The system will stay bootable.
  • cloning byte-by-byte will even work on a file system the computer does not understand, e.g. an encrypted Windows partition.
  • cloning file-by-file will allow you to deploy the system on a smaller partition
  • cloning file-by-file will not clone parts of a disk that are not part of a file


  • Compression keeps your backup small in file size. Plus it accelerates your backup procedure if you have a fast processor and a slow hard disk or network.
  • Your /boot/grub/menu.lst will list entries for a boot menu to boot from. The root device can be stated there as /dev/sda, /dev/by-id/whatever, /dev/by-uuid/whatever, /dev/mapper/whatever or some other ways to name the disk. The way that is optimal for cloning is to use the /dev/disk/by-uuid name because this name will be cloned with the disk and be the same even if deployed on another harddisk.
  • You may be using more than one partition or harddisk during normal operations. In this case you may want to clone all harddisks/partitions.

Over the network

file-by-file copy

To store a backup of one computer on the other via network, use the command:

cd /
tar -cvz $(ls | grep -v proc)  | ssh root@ "cat >slash.tar.gz"

To clone a computer over the network, say:

cd /
tar -cv $(ls | grep -v proc)  | ssh root@ "(cd /public/ubunturoot; tar xv )"

Afterwards you may want to change

  • IP address, netmask, gateway, name server, time server, hostname
  • /etc/fstab to contain generic device names like /dev/sda1 instead of /dev/disk/by-uuid/7e9e1890-312e-43eb-8ebb-82fe03b62732
  • /boot/grub/menu.lst to contain generic device names

byte-by-byte copy

This is how you can clone the harddisk of any computer, even if it is an encrypted Windows computer. Boot the computer from Knoppix, open a console, enter

dd if=/dev/sdx | bzip2 -z | ssh root@ "(cat >backup-sdx.bz2)"

Be sure to replace /dev/sdx by the harddisk you want to clone and by your target computer's IP.


file-by-file copy

Local cloning is e.g. to a USB disk to make a USB disk bootable. In this case we assume the target disk is /dev/sdx2. To clone your harddisk:

  • make sure there is no DVD, CD, network drive and other things mounted
  • mount the target harddisk to /mnt:
mount /dev/sdx2 /mnt
cd /
tar -cv $(ls | grep -v proc | grep -v sys | grep -v mnt) | ( cd /mnt; tar xv )
mkdir /mnt/proc /mnt/sys /mnt/mnt

byte-by-byte copy

This is how you can clone the harddisk of any computer locally (e.g. to a USB drive), even if it is an encrypted Windows computer.

  • boot the computer from Knoppix
  • open a console
  • mount the USB disk, e.g.
mount /dev/sdz1 /mnt/usb
  • enter
dd if=/dev/sdx | bzip2 -z | cat >/mnt/usb/backup-sdx.bz2

Be sure to replace /dev/sdx by the harddisk you want to clone.

Post cloning steps

  • If you are cloning one harddisk to another byte-by-byte to boot from the other harddisk, make sure the harddisk's ID (/dev/disk/by-id) is not in /boot/grub/menu.lst. Rather, the harddisk's UUID should be there because this will be cloned with the other data.
  • change hostname
  • change IP address
  • under some distributions, e.g. SUSE you have to re-configure networking. The IP address will be bound to an unknown network device.
  • change /etc/hosts so the computer can ping itself
  • consider changing the ssh keys ~/.ssh/id_*sa*


Your computer does not boot

If you have cloned a harddisk byte-by-byte and now booting from it does not work, check the device name you are booting from in /boot/grub/menu.lst. The device ID of your harddisk will change, but the UUID will come with the image. So make sure you boot from the device under /dev/disk/by-uuid.