bup-damage(1)						      General Commands Manual						     bup-damage(1)

NAME

       bup-damage - randomly destroy blocks of a file

SYNOPSIS

       bup damage [-n count] [-s maxsize] [--percent pct] [-S seed] [--equal]

DESCRIPTION

       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 actually work.

OPTIONS

       -n, --num=numblocks
	      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.

       -s, --size=maxblocksize
	      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.

       --percent=maxblockpercent
	      the maximum size, in percent of the original file, of each damaged block.  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.

       -S, --seed=randomseed
	      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 time.  By default, the random numbers are different every time (so you can
	      run tests in a loop and repeatedly test with different damage each time).

       --equal
	      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.)

EXAMPLE

	      # 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

	      # deliberately damage the packs
	      bup damage -n 10 -s 1 -S 0 ~/.bup/objects/pack/*.{pack,idx}

	      # recover from the damage
	      bup fsck -r

SEE ALSO

       bup-fsck(1), par2(1)

BUP

       Part of the bup(1) suite.

AUTHORS

       Avery Pennarun <apenwarr@gmail.com>.

Bup unknown-															     bup-damage(1)