git-annex/doc/walkthrough/using_ssh_remotes.mdwn
Joey Hess ef3457196a use SHA256 by default
To get old behavior, add a .gitattributes containing: * annex.backend=WORM

I feel that SHA256 is a better default for most people, as long as their
systems are fast enough that checksumming their files isn't a problem.
git-annex should default to preserving the integrity of data as well as git
does. Checksum backends also work better with editing files via
unlock/lock.

I considered just using SHA1, but since that hash is believed to be somewhat
near to being broken, and git-annex deals with large files which would be a
perfect exploit medium, I decided to go to a SHA-2 hash.

SHA512 is annoyingly long when displayed, and git-annex displays it in a
few places (and notably it is shown in ls -l), so I picked the shorter
hash. Considered SHA224 as it's even shorter, but feel it's a bit weird.

I expect git-annex will use SHA-3 at some point in the future, but
probably not soon!

Note that systems without a sha256sum (or sha256) program will fall back to
defaulting to SHA1.
2011-11-04 15:51:01 -04:00

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Markdown

So far in this walkthrough, git-annex has been used with a remote
repository on a USB drive. But it can also be used with a git remote
that is truely remote, a host accessed by ssh.
Say you have a desktop on the same network as your laptop and want
to clone the laptop's annex to it:
# git clone ssh://mylaptop/home/me/annex ~/annex
# cd ~/annex
# git annex init "my desktop"
Now you can get files and they will be transferred (using `rsync` via `ssh`):
# git annex get my_cool_big_file
get my_cool_big_file (getting UUID for origin...) (from origin...)
SHA256-s86050597--6ae2688bc533437766a48aa19f2c06be14d1bab9c70b468af445d4f07b65f41e 100% 2159 2.1KB/s 00:00
ok
When you drop files, git-annex will ssh over to the remote and make
sure the file's content is still there before removing it locally:
# git annex drop my_cool_big_file
drop my_cool_big_file (checking origin..) ok
Note that normally git-annex prefers to use non-ssh remotes, like
a USB drive, before ssh remotes. They are assumed to be faster/cheaper to
access, if available. There is a annex-cost setting you can configure in
`.git/config` to adjust which repositories it prefers. See
[[the_man_page|git-annex]] for details.
Also, note that you need full shell access for this to work --
git-annex needs to be able to ssh in and run commands. Or at least,
your shell needs to be able to run the [[git-annex-shell]] command.