# Miscellaneous Help

## borg help patterns

The path/filenames used as input for the pattern matching start from the currently active recursion root. You usually give the recursion root(s) when invoking borg and these can be either relative or absolute paths.

Starting with Borg 1.2, paths that are matched against patterns always appear relative. If you give `/absolute/` as root, the paths going into the matcher will start with `absolute/`. If you give `../../relative` as root, the paths will be normalized as `relative/`.

A directory exclusion pattern can end either with or without a slash (‘/’). If it ends with a slash, such as some/path/, the directory will be included but not its content. If it does not end with a slash, such as some/path, both the directory and content will be excluded.

Borg supports different pattern styles. To define a non-default style for a specific pattern, prefix it with two characters followed by a colon ‘:’ (i.e. `fm:path/*`, `sh:path/**`).

Fnmatch, selector fm:

  This is the default style for `--exclude` and `--exclude-from`. These patterns use a variant of shell pattern syntax, with ‘*’ matching any number of characters, ‘?’ matching any single character, ‘[…]’ matching any single character specified, including ranges, and ‘[!…]’ matching any character not specified. For the purpose of these patterns, the path separator (backslash for Windows and ‘/’ on other systems) is not treated specially. Wrap meta-characters in brackets for a literal match (i.e. [?] to match the literal character ?). For a path to match a pattern, the full path must match, or it must match from the start of the full path to just before a path separator. Except for the root path, paths will never end in the path separator when matching is attempted. Thus, if a given pattern ends in a path separator, a ‘*’ is appended before matching is attempted. A leading path separator is always removed.

Shell-style patterns, selector sh:

  This is the default style for `--pattern` and `--patterns-from`. Like fnmatch patterns these are similar to shell patterns. The difference is that the pattern may include **/ for matching zero or more directory levels, * for matching zero or more arbitrary characters with the exception of any path separator. A leading path separator is always removed.

Regular expressions, selector re:

  Regular expressions similar to those found in Perl are supported. Unlike shell patterns regular expressions are not required to match the full path and any substring match is sufficient. It is strongly recommended to anchor patterns to the start (‘^’), to the end (‘$’) or both. Path separators (backslash for Windows and ‘/’ on other systems) in paths are always normalized to a forward slash (‘/’) before applying a pattern. The regular expression syntax is described in the Python documentation for the re module.

Path prefix, selector pp:

  This pattern style is useful to match whole sub-directories. The pattern pp:root/somedir matches root/somedir and everything therein. A leading path separator is always removed.

Path full-match, selector pf:

  This pattern style is (only) useful to match full paths. This is kind of a pseudo pattern as it can not have any variable or unspecified parts - the full path must be given. pf:root/file.ext matches root/file.ext only. A leading path separator is always removed.

  Implementation note: this is implemented via very time-efficient O(1) hashtable lookups (this means you can have huge amounts of such patterns without impacting performance much). Due to that, this kind of pattern does not respect any context or order. If you use such a pattern to include a file, it will always be included (if the directory recursion encounters it). Other include/exclude patterns that would normally match will be ignored. Same logic applies for exclude.

Note

re:, sh: and fm: patterns are all implemented on top of the Python SRE engine. It is very easy to formulate patterns for each of these types which requires an inordinate amount of time to match paths. If untrusted users are able to supply patterns, ensure they cannot supply re: patterns. Further, ensure that sh: and fm: patterns only contain a handful of wildcards at most.

Exclusions can be passed via the command line option `--exclude`. When used from within a shell, the patterns should be quoted to protect them from expansion.

The `--exclude-from` option permits loading exclusion patterns from a text file with one pattern per line. Lines empty or starting with the number sign (‘#’) after removing whitespace on both ends are ignored. The optional style selector prefix is also supported for patterns loaded from a file. Due to whitespace removal, paths with whitespace at the beginning or end can only be excluded using regular expressions.

To test your exclusion patterns without performing an actual backup you can run `borg create --list --dry-run ...`.

Examples:

    # Exclude '/home/user/file.o' but not '/home/user/file.odt':
    $ borg create -e '*.o' backup /

    # Exclude '/home/user/junk' and '/home/user/subdir/junk' but
    # not '/home/user/importantjunk' or '/etc/junk':
    $ borg create -e 'home/*/junk' backup /

    # Exclude the contents of '/home/user/cache' but not the directory itself:
    $ borg create -e home/user/cache/ backup /

    # The file '/home/user/cache/important' is *not* backed up:
    $ borg create -e home/user/cache/ backup / /home/user/cache/important

    # The contents of directories in '/home' are not backed up when their name
    # ends in '.tmp'
    $ borg create --exclude 're:^home/[^/]+\.tmp/' backup /

    # Load exclusions from file
    $ cat >exclude.txt <<EOF
    # Comment line
    home/*/junk
    *.tmp
    fm:aa:something/*
    re:^home/[^/]+\.tmp/
    sh:home/*/.thumbnails
    # Example with spaces, no need to escape as it is processed by borg
    some file with spaces.txt
    EOF
    $ borg create --exclude-from exclude.txt backup /

A more general and easier to use way to define filename matching patterns exists with the `--pattern` and `--patterns-from` options. Using these, you may specify the backup roots, default pattern styles and patterns for inclusion and exclusion.

Root path prefix `R`

  A recursion root path starts with the prefix `R`, followed by a path (a plain path, not a file pattern). Use this prefix to have the root paths in the patterns file rather than as command line arguments.

Pattern style prefix `P`

  To change the default pattern style, use the `P` prefix, followed by the pattern style abbreviation (`fm`, `pf`, `pp`, `re`, `sh`). All patterns following this line will use this style until another style is specified.

Exclude pattern prefix `-`

  Use the prefix `-`, followed by a pattern, to define an exclusion. This has the same effect as the `--exclude` option.

Exclude no-recurse pattern prefix `!`

  Use the prefix `!`, followed by a pattern, to define an exclusion that does not recurse into subdirectories. This saves time, but prevents include patterns to match any files in subdirectories.

Include pattern prefix `+`

  Use the prefix `+`, followed by a pattern, to define inclusions. This is useful to include paths that are covered in an exclude pattern and would otherwise not be backed up.

Note

Via `--pattern` or `--patterns-from` you can define BOTH inclusion and exclusion of files using pattern prefixes `+` and `-`. With `--exclude` and `--exclude-from` ONLY excludes are defined.

The first matching pattern is used, so if an include pattern matches before an exclude pattern, the file is backed up. Note that a no-recurse exclude stops examination of subdirectories so that potential includes will not match - use normal excludes for such use cases.

Example:

    # Define the recursion root
    R /
    # Exclude all iso files in any directory
    - **/*.iso
    # Explicitly include all inside etc and root
    + etc/**
    + root/**
    # Exclude a specific directory under each user's home directories
    - home/*/.cache
    # Explicitly include everything in /home
    + home/**
    # Explicitly exclude some directories without recursing into them
    ! re:^(dev|proc|run|sys|tmp)
    # Exclude all other files and directories
    # that are not specifically included earlier.
    - **

Note

It’s possible that a sub-directory/file is matched while parent directories are not. In that case, parent directories are not backed up thus their user, group, permission, etc. can not be restored.

Note that the default pattern style for `--pattern` and `--patterns-from` is shell style (sh:), so those patterns behave similar to rsync include/exclude patterns. The pattern style can be set via the P prefix.

Patterns (`--pattern`) and excludes (`--exclude`) from the command line are considered first (in the order of appearance). Then patterns from `--patterns-from` are added. Exclusion patterns from `--exclude-from` files are appended last.

Examples:

    # backup pics, but not the ones from 2018, except the good ones:
    # note: using = is essential to avoid cmdline argument parsing issues.
    borg create --pattern=+pics/2018/good --pattern=-pics/2018 repo::arch pics

    # use a file with patterns:
    borg create --patterns-from patterns.lst repo::arch

The patterns.lst file could look like that:

    # "sh:" pattern style is the default, so the following line is not needed:
    P sh
    R /
    # can be rebuild
    - home/*/.cache
    # they're downloads for a reason
    - home/*/Downloads
    # susan is a nice person
    # include susans home
    + home/susan
    # also back up this exact file
    + pf:home/bobby/specialfile.txt
    # don't backup the other home directories
    - home/*
    # don't even look in /proc
    ! proc

You can specify recursion roots either on the command line or in a patternfile:

    # these two commands do the same thing
    borg create --exclude home/bobby/junk repo::arch /home/bobby /home/susan
    borg create --patterns-from patternfile.lst repo::arch

The patternfile:

    # note that excludes use fm: by default and patternfiles use sh: by default.
    # therefore, we need to specify fm: to have the same exact behavior.
    P fm
    R /home/bobby
    R /home/susan

    - home/bobby/junk

This allows you to share the same patterns between multiple repositories without needing to specify them on the command line.

## borg help placeholders

Repository (or Archive) URLs, `--prefix`, `--glob-archives`, `--comment` and `--remote-path` values support these placeholders:

{hostname}

  The (short) hostname of the machine.

{fqdn}

  The full name of the machine.

{reverse-fqdn}

  The full name of the machine in reverse domain name notation.

{now}

  The current local date and time, by default in ISO-8601 format. You can also supply your own format string, e.g. {now:%Y-%m-%d_%H:%M:%S}

{utcnow}

  The current UTC date and time, by default in ISO-8601 format. You can also supply your own format string, e.g. {utcnow:%Y-%m-%d_%H:%M:%S}

{user}

  The user name (or UID, if no name is available) of the user running borg.

{pid}

  The current process ID.

{borgversion}

  The version of borg, e.g.: 1.0.8rc1

{borgmajor}

  The version of borg, only the major version, e.g.: 1

{borgminor}

  The version of borg, only major and minor version, e.g.: 1.0

{borgpatch}

  The version of borg, only major, minor and patch version, e.g.: 1.0.8

If literal curly braces need to be used, double them for escaping:

    borg create /path/to/repo::{{literal_text}}

Examples:

    borg create /path/to/repo::{hostname}-{user}-{utcnow} ...
    borg create /path/to/repo::{hostname}-{now:%Y-%m-%d_%H:%M:%S} ...
    borg prune --glob-archives '{hostname}-*' ...

Note

systemd uses a difficult, non-standard syntax for command lines in unit files (refer to the systemd.unit(5) manual page).

When invoking borg from unit files, pay particular attention to escaping, especially when using the now/utcnow placeholders, since systemd performs its own %-based variable replacement even in quoted text. To avoid interference from systemd, double all percent signs (`{hostname}-{now:%Y-%m-%d_%H:%M:%S}` becomes `{hostname}-{now:%%Y-%%m-%%d_%%H:%%M:%%S}`).

## borg help compression

It is no problem to mix different compression methods in one repo, deduplication is done on the source data chunks (not on the compressed or encrypted data).

If some specific chunk was once compressed and stored into the repo, creating another backup that also uses this chunk will not change the stored chunk. So if you use different compression specs for the backups, whichever stores a chunk first determines its compression. See also borg recreate.

Compression is lz4 by default. If you want something else, you have to specify what you want.

Valid compression specifiers are:

none

  Do not compress.

lz4

  Use lz4 compression. Very high speed, very low compression. (default)

zstd[,L]

  Use zstd (“zstandard”) compression, a modern wide-range algorithm. If you do not explicitly give the compression level L (ranging from 1 to 22), it will use level 3. Archives compressed with zstd are not compatible with borg < 1.1.4.

zlib[,L]

  Use zlib (“gz”) compression. Medium speed, medium compression. If you do not explicitly give the compression level L (ranging from 0 to 9), it will use level 6. Giving level 0 (means “no compression”, but still has zlib protocol overhead) is usually pointless, you better use “none” compression.

lzma[,L]

  Use lzma (“xz”) compression. Low speed, high compression. If you do not explicitly give the compression level L (ranging from 0 to 9), it will use level 6. Giving levels above 6 is pointless and counterproductive because it does not compress better due to the buffer size used by borg - but it wastes lots of CPU cycles and RAM.

auto,C[,L]

  Use a built-in heuristic to decide per chunk whether to compress or not. The heuristic tries with lz4 whether the data is compressible. For incompressible data, it will not use compression (uses “none”). For compressible data, it uses the given C[,L] compression - with C[,L] being any valid compression specifier.

obfuscate,SPEC,C[,L]

  Use compressed-size obfuscation to make fingerprinting attacks based on the observable stored chunk size more difficult. Note:

  - You must combine this with encryption, or it won’t make any sense.

  - Your repo size will be bigger, of course.

  - A chunk is limited by the constant `MAX_DATA_SIZE` (cur. ~20MiB).

  The SPEC value determines how the size obfuscation works:

  Relative random reciprocal size variation (multiplicative)

  Size will increase by a factor, relative to the compressed data size. Smaller factors are used often, larger factors rarely.

  Available factors:

      1:     0.01 ..        100
      2:     0.1  ..      1,000
      3:     1    ..     10,000
      4:    10    ..    100,000
      5:   100    ..  1,000,000
      6: 1,000    .. 10,000,000

  Example probabilities for SPEC `1`:

      90   %  0.01 ..   0.1
       9   %  0.1  ..   1
       0.9 %  1    ..  10
       0.09% 10    .. 100

  Randomly sized padding up to the given size (additive)

      110: 1kiB (2 ^ (SPEC - 100))
      ...
      120: 1MiB
      ...
      123: 8MiB (max.)

Examples:

    borg create --compression lz4 REPO::ARCHIVE data
    borg create --compression zstd REPO::ARCHIVE data
    borg create --compression zstd,10 REPO::ARCHIVE data
    borg create --compression zlib REPO::ARCHIVE data
    borg create --compression zlib,1 REPO::ARCHIVE data
    borg create --compression auto,lzma,6 REPO::ARCHIVE data
    borg create --compression auto,lzma ...
    borg create --compression obfuscate,110,none ...
    borg create --compression obfuscate,3,auto,zstd,10 ...
    borg create --compression obfuscate,2,zstd,6 ...