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Creating a Backup Image of a PC This page describes how to create a complete backup image of a PC, with focus being given to imaging a Linux PC. Background Information There are many different ways to backup a PC. An offline cold backup involves taking the PC offline, with an exact copy of the contents of the HDD being made. Cold backups are typically performed using some form of software to image either the entire HDD, or each partition on the HDD. Online backups (also known as a hot backup) involve making a backup of a PC without interrupting its operation. There are many methods for achieving this on a linux box, including tar, rsync, etc. A full backup refers to a complete backup, ie, everything is backed up. Incremental backups involve only backing up the changes since the previous backup, and can provide a very efficient method to repeatedly backup a PC without creating an excessive volume of backups. There is no single "correct" way to backup a PC - it's really a matter of selecting the appropriate method that suits your requirements. This page details the process required to create a complete backup image of a PC, using freeware utilities. While the example provided below involves imaging a linux PC, the same approach can certainly be used to create a backup image of a Windows PC. The partition table will be backed up, including information about any extended partitions. Then Partition Image will be used to create a compressed image of each partition, thus consuming far less disk space than an uncompressed complete copy of each partition (such as a partition copy created using dd). Software Used A bootable CDROM called System Rescue CD is invaluable, as it contains all the tools and utilities required to manipulate partition tables, format partitions, as well as saving a partition to an image file, and restoring an image to a partition. The following utilities on the System Rescue CD are particularly useful in the context of imaging PCs: partimage - Partition Image cfdisk - Curses based disk partition table manipulator for Linux fdisk - Partition table manipulator for Linux dd - convert and copy a file sfdisk - Partition table manipulator for Linux Note that Partition Image provides functionality to image a partition to a file on a local disk, but can also create image files on another server over the network, providing you are running a partimage server on another PC. This tutorial assumes image files are being created on a local disk. Imaging the PC HDD Names Linux uses a very different naming convention than Windows for hard drives. The hard drives are named after their physical connection. Sample hard drive names are as follows: /dev/hda master device on primary IDE channel /dev/hdb slave device on primary IDE channel /dev/hdc master device on secondary IDE channel /dev/hdd slave device on secondary IDE channel /dev/sda first SCSI hard drive /dev/sdb second SCSI hard drive ... Each partition on a HDD is named by appending a number to the end of the HDD name, ie, /dev/hda1 is the first partition on /dev/hda, which is the master device on the primary IDE channel. For the purposes of this tutorial, a second HDD was added to a linux PC, to allow partitions to be imaged to the second HDD. The linux PC has the following devices: /dev/hda HDD being imaged /dev/hdc target HDD onto which images will be written /dev/hdd CDROM drive (containing SystemRescueCD) Using the System Rescue CD Boot the PC using the SystemRescueCD. When prompted for a keymap selection, just hit "Enter" to use the default speakup-us keymap (or select another if it's more appropriate). Once you have a root@sysresccd prompt, you're ready to get started. Prepare Destination Drive The destination HDD (in my case, this was /dev/hdc) must be prepared to allow images to be written to it. If this HDD already has a filesystem on it, and has sufficient space, then there should be no need to re-partition it or re-format it. Note that repartitioning the HDD will typically result in all data on it being lost. I used cfdisk to create a single 4GB FAT32 partition on /dev/hdc, and then formatted it using mkdosfs -F 32 /dev/hdc1 A FAT32 filesystem was chosen, as it will allow this partition to be read if/when the HDD is placed into a Windows PC. If you prefer an ext3 filesystem, format it using mkfs.ext3 /dev/hdc1 after creating the partition. Mount The Destination Drive To be able to access any partition on the backup drive, it must be mounted. First create a mount point: mkdir /mnt/hdc1 Then mount the target partition using the mount point: mount /dev/hdc1 /mnt/hdc1 Confirm the partition has been mounted and is available by running df -h. The output should include a line for the newly mounted partition, and should also show the amount of available space on it, similar to this: Filesystem Size Used Avail Use% Mounted on ... /dev/hdc1 4.0G 4.0K 4.0G 1% /mnt/hdc1 The above output shows that the /dev/hdc1 partition is mounted on /mnt/hdc1 and has approximately 4GB free space. Review The Source HDD The HDD being imaged (/dev/hda) has three partitions on it, namely the root partition (/), the /boot partition, and a swap partition. Below is a screenshot showing the partitions on this HDD, as displayed by cfdisk: Backup the Partition Table To backup the partition table to a file, we can use dd as follows: dd if=/dev/hda of=/mnt/hdc1/my-hda.mbr count=1 bs=512 Linux treats a filesystem or a partition as a file, and the syntax above specifies the input file to be the /dev/hda partition, and the output file is a file on our target HDD. The other parameters specify that only a single block should be copied, and we're forcing the filesize to be 512 bytes. The output filename is arbitrary, so give it a suitable name that indicates which HDD it relates to. A ".mbr" file extension indicates it contains details relating to the master boot record. Backup Extended Partition Information If you have any extended partitions on the HDD being imaged, the details of the extended partitions can be saved as follows: sfdisk -d /dev/hda > /mnt/hdc1/my-hda.sf This will dump the partition table contents into the file we specify, in a format suitable for easily rebuilding the partition table. Again, the output filename is arbitrary, so use a suitable filename. Using Partition Image To create an image of each partition, we can use Partition Image (included on the System Rescue CD), which can be started by running partimage from a command prompt. Note that when Partition Image is running, you can still get to a command prompt by hitting Alt-F2 to select virtual console #2 (there are six available virtual consoles when booting with the System Rescue CD). You can then revert back to the previous virtual console by hitting Alt-F1. Backup Each Partition In partimage, select the partition to be imaged (ie, each partition on /dev/hda except the swap partition), and specify a filename located on the previously mounted HDD (ie, /dev/hdc1 mounted as /mnt/hdc1).