bup-fsck - Online in the Cloud

PROGRAM:

NAME

bup-fsck - verify or repair a bup repository

SYNOPSIS

bup fsck [-r] [-g] [-v] [--quick] [-j jobs] [--par2-ok] [--disable-par2] [filenames...]

DESCRIPTION

bup fsck is a tool for validating bup repositories in the same way that git fsck validates
git repositories.

It can also generate and/or use "recovery blocks" using the par2(1) tool (if you have it
installed). This allows you to recover from damaged blocks covering up to 5% of your
.pack files.

In a normal backup system, damaged blocks are less important, because there tends to be
enough data duplicated between backup sets that a single damaged backup set is
non-critical. In a deduplicating backup system like bup, however, no block is ever stored
more than once, even if it is used in every single backup. If that block were to be
unrecoverable, all your backup sets would be damaged at once. Thus, it's important to be
able to verify the integrity of your backups and recover from disk errors if they occur.

WARNING: bup fsck's recovery features are not available unless you have the free par2(1)
package installed on your bup server.

WARNING: bup fsck obviously cannot recover from a complete disk failure. If your backups
are important, you need to carefully consider redundancy (such as using RAID for
multi-disk redundancy, or making off-site backups for site redundancy).

OPTIONS

-r, --repair
attempt to repair any damaged packs using existing recovery blocks. (Requires
par2(1).)

-g, --generate
generate recovery blocks for any packs that don't already have them. (Requires
par2(1).)

-v, --verbose
increase verbosity (can be used more than once).

--quick
don't run a full git verify-pack on each pack file; instead just check the final
checksum. This can cause a significant speedup with no obvious decrease in
reliability. However, you may want to avoid this option if you're paranoid. Has
no effect on packs that already have recovery information.

-j, --jobs=numjobs
maximum number of pack verifications to run at a time. The optimal value for this
option depends how fast your CPU can verify packs vs. your disk throughput. If
you run too many jobs at once, your disk will get saturated by seeking back and
forth between files and performance will actually decrease, even if numjobs is less
than the number of CPU cores on your system. You can experiment with this option
to find the optimal value.

--par2-ok
immediately return 0 if par2(1) is installed and working, or 1 otherwise. Do not
actually check anything.

--disable-par2
pretend that par2(1) is not installed, and ignore all recovery blocks.

EXAMPLES

# generate recovery blocks for all packs that don't
# have them
bup fsck -g

# generate recovery blocks for a particular pack
bup fsck -g ~/.bup/objects/pack/153a1420cb1c8*.pack

# check all packs for correctness (can be very slow!)
bup fsck

# check all packs for correctness and recover any
# damaged ones
bup fsck -r

# check a particular pack for correctness and recover
# it if damaged
bup fsck -r ~/.bup/objects/pack/153a1420cb1c8*.pack

# check if recovery blocks are available on this system
if bup fsck --par2-ok; then
echo "par2 is ok"
fi

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