path: root/doc/git-annex.mdwn

# NAME

git-annex - manage files with git, without checking their contents in

# SYNOPSIS

git annex command [params ...]

# DESCRIPTION

git-annex allows managing files with git, without checking the file
contents into git. While that may seem paradoxical, it is useful when
dealing with files larger than git can currently easily handle, whether due
to limitations in memory, checksumming time, or disk space.

Even without file content tracking, being able to manage files with git,
move files around and delete files with versioned directory trees, and use
branches and distributed clones, are all very handy reasons to use git. And
annexed files can co-exist in the same git repository with regularly
versioned files, which is convenient for maintaining documents, Makefiles,
etc that are associated with annexed files but that benefit from full
revision control.

When a file is annexed, its content is moved into a key-value store, and
a symlink is made that points to the content. These symlinks are checked into
git and versioned like regular files. You can move them around, delete 
them, and so on. Pushing to another git repository will make git-annex
there aware of the annexed file, and it can be used to retrieve its
content from the key-value store.

# EXAMPLES

	# git annex get video/hackity_hack_and_kaxxt.mov
	get video/_why_hackity_hack_and_kaxxt.mov (not available)
	  I was unable to access these remotes: server
	  Try making some of these repositories available:
	  	5863d8c0-d9a9-11df-adb2-af51e6559a49  -- my home file server
	   	58d84e8a-d9ae-11df-a1aa-ab9aa8c00826  -- portable USB drive
	   	ca20064c-dbb5-11df-b2fe-002170d25c55  -- backup SATA drive
	failed
	# sudo mount /media/usb
	# git remote add usbdrive /media/usb
	# git annex get video/hackity_hack_and_kaxxt.mov
	get video/hackity_hack_and_kaxxt.mov (copying from usbdrive...) ok
	# git commit -a -m "got a video I want to rewatch on the plane"
	
	# git annex add iso
	add iso/Debian_5.0.iso ok
	# git commit -a -m "saving Debian CD for later"
	
	# git annex drop iso/Debian_4.0.iso
	drop iso/Debian_4.0.iso ok
	# git commit -a -m "freed up space"
	
	# git annex move iso --to=usbdrive
	move iso/Debian_5.0.iso (moving to usbdrive...) ok

# COMMANDS

Like many git commands, git-annex can be passed a path that 
is either a file or a directory. In the latter case it acts on all relevant
files in the directory. If no path is specified, most git-annex commands
default to acting on all relevant files in the current directory (and
subdirectories).

Many git-annex commands will stage changes for later `git commit` by you.

* add [path ...]

  Adds files in the path to the annex. Files that are already checked into
  git, or that git has been configured to ignore will be silently skipped.

* get [path ...]

  Makes the content of annexed files available in this repository. Depending
  on the backend used, this will involve copying them from another repository,
  or downloading them, or transferring them from some kind of key-value store.

* drop [path ...]

  Drops the content of annexed files from this repository. 

  git-annex may refuse to drop content if the backend does not think
  it is safe to do so, typically because of the setting of annex.numcopies.

* move [path ...]
  
  When used with the --from option, moves the content of annexed files
  from the specified repository to the current one.

  When used with the --to option, moves the content of annexed files from
  the current repository to the specified one.

* copy [path ...]

  When used with the --from option, copies the content of annexed files
  from the specified repository to the current one.

  When used with the --to option, copies the content of annexed files from
  the current repository to the specified one.

  To avoid contacting the remote to check if it has every file, specify --fast

* unlock [path ...]

  Normally, the content of annexed files is protected from being changed.
  Unlocking a annexed file allows it to be modified. This replaces the
  symlink for each specified file with a copy of the file's content.
  You can then modify it and `git annex add` (or `git commit`) to inject
  it back into the annex.

* edit [path ...]

  This is an alias for the unlock command. May be easier to remember,
  if you think of this as allowing you to edit an annexed file.

* lock [path ...]

  Use this to undo an unlock command if you don't want to modify
  the files, or have made modifications you want to discard.

* init description

  Initializes git-annex with a description of the git repository,
  and sets up `.gitattributes` and the pre-commit hook.

* describe repository description

  Changes the description of a repository.

  The repository to describe can be specified by git remote name or
  by uuid. To change the description of the current repository, use
  "."

* initremote name [param=value ...]

  Sets up a special remote. The remote's
  configuration is specified by the parameters. If a remote
  with the specified name has already been configured, its configuration
  is modified by any values specified. In either case, the remote will be
  added to `.git/config`.

  Example Amazon S3 remote:

	initremote mys3 type=S3 encryption=none datacenter=EU

* fsck [path ...]

  With no parameters, this command checks the whole annex for consistency,
  and warns about or fixes any problems found.

  With parameters, only the specified files are checked.

  To avoid expensive checksum calculations, specify --fast

* unused

  Checks the annex for data that does not correspond to any files currently
  in the respository, and prints a numbered list of the data.

  To only show unused temp and bad files, specify --fast

  To check data on a remote that does not correspond to any files currently
  in the local repository, specify --from.

* dropunused [number ...]

  Drops the data corresponding to the numbers, as listed by the last
  `git annex unused`

  To drop the data from a remote, specify --from.

* find [path ...]

  Outputs a list of annexed files whose content is currently present.

  With no parameters, defaults to finding all files in the current directory
  and its subdirectories.

* whereis [path ...]

  Displays a list of repositories known to contain the content of the
  specified file or files.

* status

  Displays some statistics and other information, including how much data
  is in the annex.

  Some of the statistics can take a while to generate, and those
  come last. You can ctrl-c this command once it's displayed the
  information you wanted to see. Or, use --fast to only display
  the first, fast(ish) statistics.

* migrate [path ...]

  Changes the specified annexed files to store their content in the
  default backend (or the one specified with --backend). Only files whose
  content is currently available are migrated.

  Note that the content is not removed from the backend it was previously in.
  Use `git annex unused` to find and remove such content.

  Normally, nothing will be done to files already in the backend.
  However, if a backend changes the information it uses to construct a key,
  this can also be used to migrate files to use the new key format.

* map

  Helps you keep track of your repositories, and the connections between them,
  by going out and looking at all the ones it can get to, and generating a
  Graphviz file displaying it all. If the `dot` command is available, it is
  used to display the file to your screen (using x11 backend).

  Note that this only connects to hosts that the host it's run on can
  directly connect to. It does not try to tunnel through intermediate hosts.
  So it might not show all connections between the repositories in the network.

  Also, if connecting to a host requires a password, you might have to enter
  it several times as the map is being built.

  Note that this subcommand can be used to graph any git repository; it
  is not limited to git-annex repositories.

* unannex [path ...]

  Use this to undo an accidental `git annex add` command. You can use
  `git annex unannex` to move content out of the annex at any point,
  even if you've already committed it.

  This is not the command you should use if you intentionally annexed a
  file and don't want its contents any more. In that case you should use
  `git annex drop` instead, and you can also `git rm` the file.

* uninit

  Use this to stop using git annex. It will unannex every file in the
  repository, and remove all of git-annex's other data, leaving you with a
  git repository plus the previously annexed files.

* fix [path ...]

  Fixes up symlinks that have become broken to again point to annexed content.
  This is useful to run if you have been moving the symlinks around.

* pre-commit [path ...]

  Fixes up symlinks that are staged as part of a commit, to ensure they
  point to annexed content. Also handles injecting changes to unlocked
  files into the annex.

  This is meant to be called from git's pre-commit hook. `git annex init`
  automatically creates a pre-commit hook using this.

* trust [repository ...]

  Records that a repository is trusted to not unexpectedly lose
  content. Use with care.

  To trust the current repository, use "."

* untrust [repository ...]

  Records that a repository is not trusted and could lose content
  at any time.

* semitrust [repository ...]

  Returns a repository to the default semi trusted state.

* fromkey file

  This can be used to manually set up a file to link to a specified key
  in the key-value backend. How you determine an existing key in the backend
  varies. For the URL backend, the key is based on an URL to the content.

  Example:

	git annex fromkey --key=URL--http://www.archive.org/somefile somefile

* dropkey [key ...]

  This plumbing-level command drops the annexed data for the specified
  keys from this repository.

  This can be used to drop content for arbitrary keys, which do not need
  to have a file in the git repository pointing at them.

  Example:

	git annex dropkey SHA1-s10-7da006579dd64330eb2456001fd01948430572f2

* setkey file

  This plumbing-level command sets the annexed data for a key to the content of
  the specified file, and then removes the file.

  Example:

	git annex setkey --key=WORM-s3-m1287765018--file /tmp/file

* upgrade

  Upgrades the repository to current layout. Upgrades are done automatically
  whenever a newer git annex encounters an old repository; this command
  allows explcitly starting an upgrade.

* version

  Shows the version of git-annex, as well as repository version information.

# OPTIONS

* --force

  Force unsafe actions, such as dropping a file's content when no other
  source of it can be verified to still exist. Use with care.

* --fast

  Enables less expensive, but also less thorough versions of some commands.
  What is avoided depends on the command.

* --quiet

  Avoid the default verbose logging of what is done; only show errors
  and progress displays.

* --verbose

  Enable verbose logging.

* --from=repository

  Specifies a repository that content will be retrieved from, or that
  should otherwise be acted on.

  It should be specified using the name of a configured remote.

* --to=repository

  Specifies a repository that content will be sent to.

  It should be specified using the name of a configured remote.

* --exclude=glob

  Skips files matching the glob pattern. The glob is matched relative to
  the current directory.

  This option can be specified multiple times.

* --backend=name

  Specifies which key-value backend to use. This can be used when
  adding a file to the annex, or migrating a file. Once files
  are in the annex, their backend is known and this option is not
  necessary.

* --key=name

  Specifies a key to operate on.

# CONFIGURATION

Like other git commands, git-annex is configured via `.git/config`.
Here are all the supported configuration settings.

* `annex.uuid`

  A unique UUID for this repository (automatically set).

* `annex.numcopies`

  Number of copies of files to keep across all repositories. (default: 1)

* `annex.backends`

  Space-separated list of names of the key-value backends to use. 
  The first listed is used to store new files by default. 
  (default: "WORM SHA1 URL")

* `remote.<name>.annex-cost`

  When determining which repository to
  transfer annexed files from or to, ones with lower costs are preferred.
  The default cost is 100 for local repositories, and 200 for remote
  repositories.

* `remote.<name>.annex-ignore`

  If set to `true`, prevents git-annex
  from using this remote by default. (You can still request it be used
  by the --from and --to options.)

  This is, for example, useful if the remote is located somewhere
  without git-annex-shell. (For example, if it's on GitHub).
  Or, it could be used if the network connection between two
  repositories is too slow to be used normally.

* `remote.<name>.annex-uuid`

  git-annex caches UUIDs of remote repositories here.

* `remote.<name>.annex-ssh-options`

  Options to use when using ssh to talk to this remote.

* `remote.<name>.annex-rsync-options`

  Options to use when using rsync
  to or from this remote. For example, to force ipv6, and limit
  the bandwidth to 100Kbyte/s, set it to "-6 --bwlimit 100"

* `remote.<name>.annex-bup-split-options`

  Options to pass to bup split when storing content in this remote.
  For example, to limit the bandwidth to 100Kbye/s, set it to "--bwlimit 100k"
  (There is no corresponding option for bup join.)

* `annex.ssh-options`, `annex.rsync-options`, `annex.bup-split-options`

  Default ssh, rsync, and bup options to use if a remote does not have
  specific options.

* `annex.diskreserve`

  Amount of disk space to reserve. Disk space is checked when transferring
  content to avoid running out, and additional free space can be reserved
  via this option, to make space for more important content (such as git
  commit logs). Can be specified with any commonly used units, for example,
  "0.5 gb" or "100 KiloBytes"

  The default reserve is 1 megabyte.

* `annex.version`

  Automatically maintained, and used to automate upgrades between versions.

* `remote.<name>.buprepo`

  Used by bup special remotes, this configures
  the location of the bup repository to use. Normally this is automaticaly
  set up by `git annex initremote`, but you can change it if needed.

* `remote.<name>.directory`

  Used by directory special remotes, this configures
  the location of the directory where annexed files are stored for this
  remote. Normally this is automaticaly set up by `git annex initremote`,
  but you can change it if needed.

* `remote.<name>.s3`

  Used to identify Amazon S3 special remotes.
  Normally this is automaticaly set up by `git annex initremote`.

# CONFIGURATION VIA .gitattributes

The backend used when adding a new file to the annex can be configured
on a per-file-type basis via `.gitattributes` files. In the file,
the `annex.backend` attribute can be set to the name of the backend to
use. For example, this here's how to use the WORM backend by default,
but the SHA1 backend for ogg files:

	* annex.backend=WORM
	*.ogg annex.backend=SHA1

The numcopies setting can also be configured on a per-file-type basis via
the `annex.numcopies` attribute in `.gitattributes` files.
For example, this makes two copies be needed for wav files:

	*.wav annex.numcopies=2

# FILES

These files are used by git-annex, in your git repository:

`.git/annex/objects/` contains the annexed file contents that are currently
available. Annexed files in your git repository symlink to that content.

`.git-annex/uuid.log` is used to map between repository UUID and
descriptions.

`.git-annex/trust.log` is used to indicate which repositories are trusted
and untrusted.

`.git-annex/*.log` is where git-annex records its content tracking
information. These files should be committed to git.

`.gitattributes` is configured to use git's union merge driver
to avoid conflicts when merging files in the `.git-annex` directory.

# SEE ALSO

Most of git-annex's documentation is available on its web site, 
<http://git-annex.branchable.com/>

If git-annex is installed from a package, a copy of its documentation
should be included, in, for example, `/usr/share/doc/git-annex/`

# AUTHOR

Joey Hess <joey@kitenet.net>

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

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