This simple utility was created to reduce size of backup images of disk
partitions. It is intended to be used in conjunction with dd or similar
utility. The primary concern is safe operation, so diff-dd performs many
checks of the input and output files. For example, the differential image file
is read twice when restoring it. Because of that, it is slower.
diff-dd help
diff-dd backup [-s SECTOR_SIZE] [-b BUFFER_SIZE] INFILE REFFILE OUTFILE
diff-dd restore [-s SECTOR_SIZE] [-b BUFFER_SIZE] INFILE OUTFILE
Using diff-dd for backup requires the full backup image to
exist. Differential backup is created with:
diff-dd backup INFILE REFFILE OUTFILE
The INFILE is a path to the file to backup differentially, the
REFFILE is the full image, and the OUTFILE is the file to
which only the changed sectors of the INFILE, compared to the
REFFILE, and their offsets will be saved.
The restoration means application of the changed sectors saved in the
INFILE, which is the differential image, to the OUTFILE:
diff-dd restore INFILE OUTFILE
-s sets the sector size by which the files will be processed
(default is 512 B). It can be used to control granularity of
differential backup.
-b sets the size of the buffer for the sectors of the input and
output file (default is 4 MiB). The input data is always buffered. The
output data are buffered only in backup mode.
First, the full image of the partition to backup has to be created:
dd bs=4M if=/dev/sda1 of=full.img
When the user decides to create the differential image, he or she runs:
diff-dd backup /dev/sda1 full.img diff.img
If a data accident happens, the partition can be restored by running:
dd bs=4M if=full.img of=/dev/sda1
diff-dd restore diff.img /dev/sda1
The first command restores the old full image. The second one applies the differences.