git-annex can transfer data to and from configured git remotes. Normally those remotes are normal git repositories (bare and non-bare; local and remote), that store the file contents in their own git-annex directory.

But, git-annex also extends git's concept of remotes, with these special types of remotes. These can be used just like any normal remote by git-annex. They cannot be used by other git commands though.

The above special remotes are built into git-annex, and can be used to tie git-annex into many cloud services.

Here are specific instructions for using git-annex with various services:

Want to add support for something else? Write your own!

Ways to use special remotes

There are many use cases for a special remote. You could use it as a backup. You could use it to archive files offline in a drive with encryption enabled so if the drive is stolen your data is not. You could git annex move --to specialremote large files when your local drive is getting full, and then git annex move the files back when free space is again available. You could have one repository copy files to a special remote, and then git annex get them on another repository, to transfer the files between computers that do not communicate directly.

The git-annex assistant makes it easy to set up rsync remotes using this last scenario, which is referred to as a transfer repository, and arranges to drop files from the transfer repository once they have been transferred to all known clients.

None of these use cases are particular to particular special remote types. Most special remotes can all be used in these and other ways. It largely doesn't matter for your use what underlying transport the special remote uses.

Unused content on special remotes

Over time, special remotes can accumulate file content that is no longer referred to by files in git. Normally, unused content in the current repository is found by running git annex unused. To detect unused content on special remotes, instead use git annex unused --from. Example:

$ git annex unused --from mys3
unused mys3 (checking for unused data...) 
  Some annexed data on mys3 is not used by any files in this repository.
    1       WORM-s3-m1301674316--foo
  (To see where data was previously used, try: git log --stat -S'KEY')
  (To remove unwanted data: git-annex dropunused --from mys3 NUMBER)
$ git annex dropunused --from mys3 1
dropunused 12948 (from mys3...) ok

Testing special remotes

To make sure that a special remote is working correctly, you can use the git annex testremote command. This expects you to have set up the remote as usual, and it then runs a lot of tests, using random data. It's particularly useful to test new implementations of special remotes.

By default it will upload and download files of around 1MiB to the remote it tests; the --size parameter can adjust it test using smaller files.

It's safe to use this command even when you're already storing data in a remote; it won't touch your existing files stored on the remote.

For most remotes, it also won't bloat the remote with any data, since it cleans up the stuff it uploads. However, the bup, ddar, and tahoe special remotes don't support removal of uploaded files, so be careful with those.