bup-damage(1)

1bup-damage(1)                                                    bup-damage(1)
2
3
4

NAME

6       bup-damage - randomly destroy blocks of a file
7

SYNOPSIS

9       bup  damage [-n count] [-s maxsize] [--percent pct] [-S seed] [--equal]
10       <filenames...>
11

DESCRIPTION

13       Use bup damage to deliberately destroy blocks in a .pack or  .idx  file
14       (from  .bup/objects/pack)  to test the recovery features of bup-fsck(1)
15       or other programs.
16
17       THIS PROGRAM IS EXTREMELY DANGEROUS AND WILL DESTROY YOUR DATA
18
19       bup damage is primarily useful for automated or manual  tests  of  data
20       recovery tools, to reassure yourself that the tools actually work.
21

OPTIONS

23       -n, --num=numblocks
24              the  number  of  separate blocks to damage in each file (default
25              10).  Note that it's possible for more than one damaged  segment
26              to fall in the same bup-fsck(1) recovery block, so you might not
27              damage as many recovery blocks as you  expect.   If  this  is  a
28              problem, use --equal.
29
30       -s, --size=maxblocksize
31              the maximum size, in bytes, of each damaged block (default 1 un‐
32              less --percent is specified).  Note  that  because  of  the  way
33              bup-fsck(1) works, a multi-byte block could fall on the boundary
34              between two recovery blocks, and thus damaging two separate  re‐
35              covery blocks.  In small files, it's also possible for a damaged
36              block to be larger than a recovery block.  If these issues might
37              be  a  problem,  you  should  use the default damage size of one
38              byte.
39
40       --percent=maxblockpercent
41              the maximum size, in percent of the original file, of each  dam‐
42              aged block.  If both --size and --percent are given, the maximum
43              block size is the minimum of the two restrictions.  You can  use
44              this  to  ensure  that a given block will never damage more than
45              one or two git-fsck(1) recovery blocks.
46
47       -S, --seed=randomseed
48              seed the random number generator with the given value.   If  you
49              use  this  option, your tests will be repeatable, since the dam‐
50              aged block offsets, sizes, and contents will be the  same  every
51              time.   By  default, the random numbers are different every time
52              (so you can run tests in a loop and repeatedly test with differ‐
53              ent damage each time).
54
55       --equal
56              instead of choosing random offsets for each damaged block, space
57              the blocks equally throughout the file, starting  at  offset  0.
58              If  you also choose a correct maximum block size, this can guar‐
59              antee that any given damage block never damages  more  than  one
60              git-fsck(1) recovery block.  (This is also guaranteed if you use
61              -s 1.)
62

EXAMPLES

64              # make a backup in case things go horribly wrong
65              cp -pPR ~/.bup/objects/pack ~/bup-packs.bak
66
67              # generate recovery blocks for all packs
68              bup fsck -g
69
70              # deliberately damage the packs
71              bup damage -n 10 -s 1 -S 0 ~/.bup/objects/pack/*.{pack,idx}
72
73              # recover from the damage
74              bup fsck -r
75

BUP

80       Part of the bup(1) suite.
81

AUTHORS

83       Avery Pennarun <apenwarr@gmail.com>.
84
85
86
87Bup 0.29.1                        2017-03-26                     bup-damage(1)