git-annex-preferred-content(1)

NAME
git-annex-preferred-content - which files are wanted in a repository

DESCRIPTION
Each repository has a preferred content setting, which specifies content that the repository wants to have present. These settings can be configured using git annex vicfg or git annex wanted. They are used by the --auto option, by git annex sync --content, by clusters, and by the git-annex assistant.

While preferred content expresses a preference, it can be overridden by simply using git annex drop. On the other hand, required content settings are enforced; git annex drop will refuse to drop a file if doing so would violate its required content settings. A repository's required content can be configured using git annex vicfg or git annex required.

SYNTAX
Preferred content expressions use a similar syntax to the git-annex-matching-options(1), without the dashes. For example:

 exclude=archive/* and (include=*.mp3 or smallerthan=1mb)

The idea is that you write an expression that files are matched against. If a file matches, the repository wants to store its content. If it doesn't, the repository wants to drop its content (if there are enough copies elsewhere to allow removing it).

An empty preferred content expression is treated the same as preferred content not being configured.

EXPRESSIONS

include=glob / exclude=glob

    Match files to include, or exclude.

    While the command-line options --include=glob and --exclude=glob match files relative to the current directory, preferred content expressions match files relative to the top of the git repository.

    A glob is something like foo.* or b?r. Globs can also contain character classes, like foo[Bb]ar, as well as additional POSIX character classes like [[:space:]]. Which is useful, since a glob in a preferred content expression cannot contain spaces. See the glob(7) man page for more about globs.

    For example, suppose you put files into archive directories when you're done with them. Then you could configure your laptop to prefer to not retain those files, like this: exclude=*/archive/*

    When a subdirectory is being exported or imported to a special remote (see git-annex-export(1)) and git-annex-import(1), these match relative to the top of the subdirectory.

    Note that, when a command is run with the --all option, or in a bare repository, there is no filename associated with an annexed object, and so "include=" and "exclude=" will not match.

copies=number
    Matches only files that git-annex believes to have the specified number of copies, or more. Note that it does not check remotes to verify that the copies still exist.

    To decide if content should be dropped, git-annex evaluates the preferred content expression under the assumption that the content has *already* been dropped. If the content would not be wanted then, the drop can be done. So, for example, copies=2 in a preferred content expression lets content be dropped only when there are currently 3 copies of it, including the repo it's being dropped from. This is different than running git annex drop --copies=2, which will drop files that currently have 2 copies.

copies=trustlevel:number
    Matches only files that git-annex believes have the specified number copies, on remotes with the specified trust level. For example, copies=trusted:2

    To match any trust level at or higher than a given level, use trustlevel+. For example, copies=semitrusted+:2

copies=groupname:number
    Matches only files that git-annex believes have the specified number of copies, on remotes in the specified group. For example, copies=archive:2

    Preferred content expressions have no equivalent to the --in option, but groups can accomplish similar things. You can add repositories to groups, and match against the groups in a preferred content expression. So rather than --in=usbdrive, put all the USB drives into a "transfer" group, and use copies=transfer:1

lackingcopies=number
    Matches only files that git-annex believes need the specified number or more additional copies to be made in order to satisfy their numcopies settings.

approxlackingcopies=number
    Like lackingcopies, but does not look at .gitattributes annex.numcopies settings. This makes it significantly faster.

inbackend=backendname
    Matches only files whose content is stored using the specified key-value backend.

    See git-annex-backends(1) for information about available backends.

securehash
    Matches only files whose content is hashed using a cryptographically secure function.

inallgroup=groupname
    Matches only files that git-annex believes are present in all repositories in the specified group.

onlyingroup=groupname
    Matches files that git-annex believes are present in at least one repository that is in the specified group, and are not present in any repositories that are not in the specified group.

smallerthan=size / largerthan=size
    Matches only files whose content is smaller than, or larger than the specified size.

    The size can be specified with any commonly used units, for example, "0.5 gb" or "100 KiloBytes"

metadata=field=glob
    Matches only files that have a metadata field attached with a value that matches the glob. The values of metadata fields are matched case insensitively.

    A glob is something like foo.* or b?r. Globs can also contain character classes, like foo[Bb]ar, as well as additional POSIX character classes like [[:space:]]. Which is useful, since a glob in a preferred content expression cannot contain spaces. See the glob(7) man page for more about globs.

    To match a tag "done", use metadata=tag=done

    To match author metadata, use metadata=author=*Smith

metadata=field<number / metadata=field>number

metadata=field<=number / metadata=field>=number
    Matches only files that have a metadata field attached with a value that is a number and is less than or greater than the specified number.

    To match PDFs with between 100 and 200 pages (assuming something has set that metadata), use metadata=pagecount>=100 and metadata=pagecount<=200

url=glob
    Matches when the content is recorded as being present in an url that matches the glob.

present
    Makes content be wanted if it's present, but not otherwise.

    This leaves it up to you to use git-annex manually to move content around. You can use this to avoid preferred content settings from affecting a subdirectory. For example: auto/* or (include=ad-hoc/* and present)

    Note that not present is not a reasonable thing to put in a preferred content expression. It says to get content that's not present, but then drop it! If that somehow gets into a preferred content expression, git-annex will recognize that the preferred content expression is not stable, and make it never match.

inpreferreddir
    Makes content be preferred if it's in a directory (located anywhere in the tree) with a particular name.

    The name of the directory can be configured using git annex enableremote $remote preferreddir=$dirname

    (If no directory name is configured, it uses "public" by default.)

    Note that, when a command is run with the --all option, or in a bare repository, there is no filename associated with an annexed object, and so "inpreferreddir" will not match.

standard
    git-annex comes with some built-in preferred content expressions, that can be used with repositories that are in some standard groups such as "client" and "transfer".

    When a repository is in exactly one such group, you can use the "standard" keyword in its preferred content expression, to match whatever content the group's expression matches.

    Most often, the whole preferred content expression is simply "standard". But, you can do more complicated things, for example: standard or include=otherdir/*

groupwanted
    The "groupwanted" keyword can be used to refer to a preferred content expression that is associated with a group, as long as there is exactly one such expression amoung the groups a repository is in. This is like the "standard" keyword, but you can configure the preferred content expressions using git annex groupwanted.

    When writing a groupwanted preferred content expression, you can use all the keywords documented here, including "standard". (But not "groupwanted".)

    For example, to make a variant of the standard client preferred content expression that does not want files in the "out" directory, you could run: git annex groupwanted client "standard and exclude=out/*"

    Then repositories that are in the client group and have their preferred content expression set to "groupwanted" will use that, while other client repositories that have their preferred content expression set to "standard" will use the standard expression.

    Or, you could make a new group, with your own custom preferred content expression tuned for your needs, and every repository you put in this group and make its preferred content be "groupwanted" will use it.

    For example, the archive group only wants to archive 1 copy of each file, spread among every repository in the group. Here's how to configure a group named redundantarchive, that instead wants to contain 3 copies of each file:

     git annex groupwanted redundantarchive "not (copies=redundantarchive:3)"
     for repo in foo bar baz; do
         git annex group $repo redundantarchive
         git annex wanted $repo groupwanted
     done

unused
    Matches only keys that git annex unused has determined to be unused.

    This is related the the --unused option. However, putting unused in a preferred content expression doesn't make git-annex consider those unused keys. So when git-annex is only checking preferred content expressions against files in the repository (which are obviously used), unused in a preferred content expression won't match anything.

    So when is unused useful in a preferred content expression?

    Using git annex sync --content --all will operate on all files, including unused ones, and take unused in preferred content expressions into account.

    The git-annex assistant periodically scans for unused files, and moves them to some repository whose preferred content expression says it wants them. (Or, if annex.expireunused is set, it may just delete them.)

balanced=groupname[:number|:lackingcopies]
    Makes content be evenly balanced amoung repositories in the group.

    The number is the number of repositories in the group that will want each file. When not specified, the default is 1.

    For example, "balanced=backup:2", when there are 3 members of the backup group, will make each backup repository want 2/3rds of the files.

    Using "lackingcopies" rather than a number makes each file be balanced amoung as many repositories in the group as are needed to satisfy its numcopies configuration. Eg, "balanced=backup:lackingcopies", when numcopies is 3 and there is 1 other copy will behave the same as "balanced=backup:2".

    For balancing to work, each repository in the group should have its preferred content set to the same expression. Using groupwanted is a good way to do that.

    The sizes of files are not taken into account, so it's possible for one repository to get larger than usual files and so fill up before the other repositories. But files are only wanted by repositories that have enough free space to hold them. So once a repository is full, the remaining repositories will have any additional files balanced amoung them. For git-annex to know when a repository is full, you must use git-annex-maxsize(1) to specify the size of each repository in the group.

    This usually avoids moving files between repositories, even if that means that things are not optimally balanced. Some of the ways that it can get out of balance include adding a new repository to the group, or a file getting copied into more repositories in the group than the specified number, or some of the repositories filling up.

    Running git-annex commands with the --rebalance option will make this expression instead behave like the fullybalanced expression, which will make repositories want to move files around as necessary in order to get fully balanced.

    Using this in a preferred content expression makes git-annex need to do some additional work to keep track of how full repositories are. Usually that won't affect performance much. However, the first time git-annex processes this expression in a given git repository, it will need to calculate the sizes of all repositories, which can be slow when there are a lot of files. When this causes git-annex to do a lot of work, it will display "(calculating repository sizes)".

    Note that not balanced not a reasonable thing to use in a preferred content expression for the same reasons as not present.

fullybalanced=groupname[:number|:lackingcopies]
    This is like balanced, but allows moving content between repositories in the group at any time to keep it fully balanced.

    Normally "balanced=groupname:number" is the same as "(fullybalanced=groupname:number and not copies=groupname:number) or present"

    When the --rebalance option is used, balanced is the same as fullybalanced.

    When the specified number is greater than 1, and too many repositories in the group are more than 90% full (as configured by annex.fullybalancedthreshhold), this behaves like fullysizebalanced.

    For example, fullybalanced=foo:3, when group foo has 5 repositories, two 50% full and three 99% full, will make some content move from the full repositories to the others. Moving content like that is expensive, but it allows new files to continue to be stored on the specified number of repositories.

sizebalanced=groupname[:number|:lackingcopies]
    Distributes content amoung repositories in the group, keeping repositories proportionally full.

    The number is the number of repositories in the group that will want each file. When not specified, the default is 1.

    For this to work, you must use git-annex-maxsize(1) to specify the size of each repository in the group. When a repository's maxsize has not been specified, it will not want any files.

    For example, if one repository in the group has a maximum size of 100 gb with 60 gb used, and another has a maximum size of 50 gb with 25 gb used, the smaller one will want files (that fit in it), and the larger one won't want any files (that would fit in the smaller one) until the smaller one gets equally full.

    Note that, once a repository contains a file, it will continue to want it, even if it's more full than other repositories. This is to avoid churn in moving files around.

    This is more likely to get out of balance than the balanced= expression is, because git-annex does not always have a consistent knowledge of how full repositories are. Consider for example if a laptop and a desktop are each sending a new file to the group. They will both pick whichever repository was least full, but that means both files go to the same repository, when a better solution might have been to send the smaller file to a different repository. When using balanced= in the same situation, it's less likely that a repository will want both files.

    Running git-annex commands with the --rebalance option will make this expression instead behave like the fullysizebalanced expression, which will make repositories want to move files around as necessary in order to get fully balanced.

    Note that not sizebalanced not a reasonable thing to use in a preferred content expression for the same reasons as not present.

fullysizebalanced=groupname[:number|:lackingcopies]
    This is like sizebalanced, but allows moving content between repositories in the group at any time to keep it fully balanced.

    Normally "sizebalanced=groupname:number" is the same as "(fullysizebalanced=groupname:number and not copies=groupname:number) or present"

    When the --rebalance option is used, sizebalanced is the same as fullysizebalanced.

anything
    Always matches.

nothing
    Never matches. (Same as "not anything")

not expression
    Inverts what the expression matches. For example, not include=archive/* is the same as exclude=archive/*

and / or / ( expression )
    These can be used to build up more complicated expressions.

TESTING
To check at the command line which files are matched by a repository's preferred content settings, you can use the --want-get and --want-drop options.

For example, git annex find --want-get --not --in . will find all the files that git annex get --auto will want to get, and git annex find --want-drop --in . will find all the files that git annex drop --auto will want to drop.

The --explain option can be used to understand why a complex preferred content expression matches or fails to match. The expression will be displayed, with each term followed by "[TRUE]" or "[FALSE]" to indicate the value. Irrelevant terms will be ommitted from the explanation, for example "exclude=* and copies=1" will be displayed as "exclude=*[FALSE]"

SEE ALSO
git-annex(1)

git-annex-vicfg(1)

git-annex-wanted(1)

git-annex-maxsize(1)

<https://git-annex.branchable.com/preferred_content/>

<https://git-annex.branchable.com/preferred_content/standard_groups/>

AUTHOR
Joey Hess <id@joeyh.name>

<http://git-annex.branchable.com/>