Thursday, 6 July 2017

Creating and restoring a block level backup of a disk with dd and par2

Let's firstly take an image of the disk / partition we wish to backup by piping it into a gzip archive:

dd if=/dev/sda1 bs=64K | gzip -9 -c > /tmp/backup.img.gz; sync

For parity we need to ensure par2 is installed with:

sudo yum -y par2cmdline

cd /tmp
par2 create backup.img.gz

Which by default will provide 5% redundancy and a recovery block count of 100.

We could alternativley use a custom level with:

par2 create -s500000 -r10 backup.img.gz

Where the recovery is set at 10% with a block size of 500KB.

We can then restore the partition with:

gzip -dc /tmp/backup.img.gz | dd of=/dev/sda1; sync

The 'd' switch instructs gzip to decompress file archive, while the 'c' switch instructs gzip to write the output to stdout so we can pipe it into dd for processing.

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