HDD or partition backup with dd

full hard disk copy

dd if=/dev/hdx of=/dev/hdy
dd if=/dev/hdx of=/path/to/image
dd if=/dev/hdx | gzip > /path/to/image.gz

Hdx could be hda, hdb etc. In the second example gzip is used to compress the image if it is really just a backup.

Restore Backup of hard disk copy

dd if=/path/to/image of=/dev/hdx
gzip -dc /path/to/image.gz | dd of=/dev/hdx

Getting around file size limitations using split

When making images, it's quite easy to run up against various file size limitations. One way to work around a given file size limitation is to use the split command.

# dd if=/dev/hda1 | gzip -c | split -b 2000m - /mnt/hdc1/backup.img.gz.

1. This example is using dd to take an image of the first partition on the first harddrive.
2. The results are passed through to gzip for compression
   • The -c option switch is used to output the result to stdout.
3. The compressed image is then piped to the split tool
   • The -b 2000m switch tells split how big to make the individual files. You can use k and m to tell switch kilobytes and megabytes (this option uses bytes by default).
   • The - option tells split to read from stdin. Otherwise, split would interpret the /mnt/hdc1... as the file to be split.
   • The /mnt/hdc1... is the prefix for the created files. Split will create files named backup.img.gz.aa, backup.img.gz.ab, etc.

To restore the multi-file backup, do the following:

# cat /mnt/hdc1/backup.img.gz.* | gzip -dc | dd of=/dev/hda1

1. Cat recombines contents of the compressed and split image files to stdout, in order.
2. Results are piped through gzip for decompression.
3. And are then written to the first partition of the hard drive with dd.