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March 15, 2011

copy partition with dd

Filed under: Linux — Tags: — admin @ 6:28 pm

HDD or partition backup with dd
full hard disk copy

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

sdx could be sda, sdb 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/sdx
gzip -dc /path/to/image.gz | dd of=/dev/sdx

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/sda1 | gzip -c | split -b 2000m – /mnt/sdc1/backup.img.gz.
This example is using dd to take an image of the first partition on the first harddrive.
The results are passed through to gzip for compression
The -c option switch is used to output the result to stdout.
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/sdc1/backup.img.gz.* | gzip -dc | dd of=/dev/sda1
Cat recombines contents of the compressed and split image files to stdout, in order.
Results are piped through gzip for decompression.
And are then written to the first partition of the hard drive with dd.

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