Section 11.5. Alt-Boot Partition Image Method

11.5. Alt-Boot Partition Image Method

This example uses dd to back up and recover a complete system at the partition level. It requires the system to be offline (booted into Knoppix), and it works regardless of your operating system. It's slightly more complex than the alt-boot full image method and still requires the system to be down during a backup, but it can be faster if your disk is partitioned correctly. You can save a lot of space and time if you partition your hard disk so that one partition contains the operating system and applications, and then apply this procedure only to that partition. (You would back up the other partitions with regular filesystem backup tools.)

11.5.1. Create the Bare-Metal Backup

Use the following steps to create a bare-metal backup of your system.

11.5.1.1. Back up the important metadata

Back up the MBR by running the following command:

# dd if=/dev/hda of=/backups/mbr bs=512 count =1

11.5.1.2. Boot the system from alternate media

Place the Knoppix CD into the drive and reboot into Knoppix. By default, Knoppix starts KDE (a windowing environment) as user knoppix. After switching to the root user (which has no password initially), create a mount point and mount an NFS directory as /backups:

knoppix@0[knoppix]$ su - # mkdir /backups # mount nfsserver:/data08/curtis /backups

See the previous section "Assumptions"if either DHCP or NFS isn't available.

11.5.1.3. Back up the operating system with a native utility

You then back up the operating system to the NFS directory using dd. You can find which partitions you need and back up just those partitions using these commands:

# fdisk -l Disk /dev/hda: 41.1 GB, 41174138880 bytes 255 heads, 63 sectors/track, 5005 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes    Device Boot      Start         End      Blocks   Id  System /dev/hda1   *           1          13      104391   83  Linux /dev/hda2              14        4874    39045982+  83  Linux /dev/hda3            4875        5005     1052257+  82  Linux swap / Solaris # dd if=/dev/hda1 of=/backups/hda1.dd # dd if=/dev/hda2 of=/backups/hda2.dd

In our example, we did not back up /dev/hda3 because it is the swap partition and has no data.

Alternatively, you can also use compression. Depending on where your bottlenecks are, this may speed things up or slow them down.

# dd if=/dev/hda1| gzip c > of=/backups/hda1.dd.gz # dd if=/dev/hda2| gzip c > of=/backups/hda2.dd.gz

You can place an & (ampersand) at the end to allow the backups to occur simultaneously by placing them in the background. However, this requires you to monitor those processes to ensure that they complete before you reboot.

11.5.2. Perform a Bare-Metal Recovery

Use the following steps to recover your system from bare metal.

11.5.2.1. Boot the system from alternate media

The first step in recovering this system is to place the Knoppix CD into the CD drive and boot up the system. A check of the partition table at this point shows the following:

# fdisk -l Disk /dev/hda: 41.1 GB, 41174138880 bytes 16 heads, 63 sectors/track, 79780 cylinders Units = cylinders of 1008 * 512 = 516096 bytes Disk /dev/hda doesn't contain a valid partition table 

As before, open a terminal window and switch to the root user, then mount your NFS directory:

knoppix@0[knoppix]$ su - # mkdir /backups # mount nfsserver:/data08/curtis /backups

See the previous section "Assumptions"if either DHCP or NFS isn't available.

11.5.2.2. Restore the boot block and prepare the new root drive

For restoring by partition, you need to restore the MBR and partition table and then restore each partition. You can restore the MBR and partition table by running the following command:

# dd if=/backups/mbr of=/dev/hda bs=512 count =1

In order to get Knoppix to recognize without a reboot that we had recovered the MBR, we found it was necessary to actually run fdisk /dev/hda and then choose w to write the partition to disk. A reboot works as well but takes longer.

11.5.2.3. Restore the operating system

You are now ready to actually restore the operating system. Use dd in the reverse order that you used to back up the operating system:

# dd if=/backups/hda1.dd of=/dev/hda1 # dd if=/backups/hda2.dd of=/dev/hda2

If you used the compression option in the backup, you should use these commands:

# gzip dc /backups/hda1.dd.gz |dd of=/dev/hda1 # gzip dc /backups/hda2.dd.gz |dd of=/dev/hda2

Again, we knew that there was nothing of value in /dev/hda3.

You can place an & at the end to allow the restores to occur simultaneously by placing them in the background. However, this requires you to monitor those processes to ensure that they complete before you reboot.

All you have to do now is remove the Knoppix CD and reboot.