How to Image-Back Up a Unix System

The "dd" command can be used to create an exact replica of your Unix system. This command can be used to copy one disk to another disk, or it can be used to create an image for storage. The image will be exactly the same size as your hard drive or partition. If you want a smaller file, you can pipe (pass) the dd command through a compression utility such as "gzip."

Things You'll Need

• Operating system CD or Linux Live CD

Instructions

1. Shut down the computer.

2. Boot to the operating system CD-ROM or a Linux Live CD. A Linux Live CD is a complete instance of the Linux operating system that runs completely from a CD-ROM.

3. Open a terminal if using a Linux Live CD. You will already be at the terminal if you are booting from an operating system CD-ROM.

4. Type the command "dd if=/dev/sda of=/dev/sdb/backup.img" to create a byte-by-byte backup image of the Unix system. Change "sda" to reflect the location of your root partition or hard drive if the operating system completely resides on one hard drive. Change "sdb" to reflect the location where you want to store the backup image.

5. Reboot the system when the "dd" command is finished.

Tips & Warnings

• You can create a compressed image with the command "dd if=/dev/sda | gzip -c > /mnt/sdb/backup.img". You must mount (prepare for use) the second hard drive before issuing this command.

• You can use a Linux Live CD and the dd command to copy any operating system.

• You must use the dd command on a drive that is unmounted (not in use).

• Be careful using this command. If not used correctly, it can erase your entire operating system.

References

• Softpanorama: Unix dd Command
• Debian Help: Back Up an Entire Hard Drive Using the dd Command
• Image Your Hard Drive Using dd

Resources

• Knoppix Live CD