Use bup damage to deliberately destroy blocks in a
.pack or .idx file (from
.bup/objects/pack) to test the recovery features of
bup-fsck(1) or other programs.
THIS PROGRAM IS EXTREMELY DANGEROUS AND WILL DESTROY YOUR DATA
bup damage is primarily useful for automated or manual
tests of data recovery tools, to reassure yourself that the tools
the number of separate blocks to damage in each file (default 10).
Note that it's possible for more than one damaged segment to fall
in the same bup-fsck(1) recovery block, so you might not
damage as many recovery blocks as you expect.
If this is a problem, use --equal.
the maximum size, in bytes, of each damaged block (default 1 unless
--percent is specified).
Note that because of the way bup-fsck(1) works, a
multi-byte block could fall on the boundary between two recovery
blocks, and thus damaging two separate recovery blocks.
In small files, it's also possible for a damaged block to be larger
than a recovery block.
If these issues might be a problem, you should use the default
damage size of one byte.
the maximum size, in percent of the original file, of each damaged
If both --size and --percent are given, the
maximum block size is the minimum of the two restrictions.
You can use this to ensure that a given block will never damage
more than one or two git-fsck(1) recovery blocks.
seed the random number generator with the given value.
If you use this option, your tests will be repeatable, since the
damaged block offsets, sizes, and contents will be the same every
By default, the random numbers are different every time (so you can
run tests in a loop and repeatedly test with different damage each
instead of choosing random offsets for each damaged block, space
the blocks equally throughout the file, starting at offset 0.
If you also choose a correct maximum block size, this can guarantee
that any given damage block never damages more than one
git-fsck(1) recovery block.
(This is also guaranteed if you use -s 1.)
# make a backup in case things go horribly wrong
cp -a ~/.bup/objects/pack ~/bup-packs.bak
# generate recovery blocks for all packs
bup fsck -g