borg-patterns - Details regarding patterns

NAME  DESCRIPTION  AUTHOR 

NAME

borg-patterns − Details regarding patterns

DESCRIPTION

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.

If you give /absolute/ as root, the paths going into the matcher will look relative like absolute/.../file.ext, because file paths in Borg archives are always stored normalized and relative. This means that e.g. borg create /path/to/repo ../some/path will store all files as some/path/.../file.ext and borg create /path/to/repo /home/user will store all files as home/user/.../file.ext.

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.

File patterns support these styles: fnmatch, shell, regular expressions, path prefixes and path full−matches. By default, fnmatch is used for −−exclude patterns and shell−style is used for the −−pattern option. For commands that support patterns in their PATH argument like (borg list), the default pattern is path prefix.

Starting with Borg 1.2, discovered fs paths are normalised, have leading slashes removed and then are matched against your patterns. Note: You need to review your include / exclude patterns and make sure they do not expect leading slashes. Borg can only deal with this for some very simple patterns by removing leading slashes there also.

If followed by a colon (':') the first two characters of a pattern are used as a style selector. Explicit style selection is necessary when a non−default style is desired or when the desired pattern starts with two alphanumeric characters followed by a colon (i.e. aa:something/*).
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 (starting points) and patterns for inclusion/exclusion. A root path starts with the prefix R, followed by a path (a plain path, not a file pattern). An include rule starts with the prefix +, an exclude rule starts with the prefix −, an exclude−norecurse rule starts with !, all followed by a pattern.

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.

Inclusion patterns are useful to include paths that are contained in an excluded path. The first matching pattern is used so if an include pattern matches before an exclude pattern, the file is backed up. If an exclude−norecurse pattern matches a directory, it won't recurse into it and won't discover any potential matches for include rules below that directory.

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.

AUTHOR

The Borg Collective


Updated 2023-01-10 - jenkler.se | uex.se