bup-fsck(1) Bup 0.33.10+
Author: Avery Pennarun apenwarr@gmail.com
Date: 2026-01-28

# 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

# SEE ALSO

`bup-damage`(1), `fsck`(1), `git-fsck`(1)

# BUP

Part of the `bup`(1) suite.