112 lines
4.5 KiB
Markdown
112 lines
4.5 KiB
Markdown
This special remote type lets you store content in a remote of your own
|
|
devising, configured via some simple hooks.
|
|
|
|
It's not recommended to use this remote type when another like [[rsync]]
|
|
or [[directory]] will do. If your hooks are not carefully written, data
|
|
could be lost.
|
|
|
|
If you're building a special remote for others to use,
|
|
instead consider building an [[external_special_remote|external]].
|
|
|
|
## example
|
|
|
|
Here's a simple example that stores content on clay tablets. If you
|
|
implement this example in the real world, I'd appreciate a tour
|
|
next Apert! :) --[[Joey]]
|
|
|
|
# git config annex.cuneiform-store-hook 'tocuneiform < "$ANNEX_FILE" | tablet-writer --implement=stylus --title="$ANNEX_KEY" | tablet-proofreader | librarian --shelve --floor=$ANNEX_HASH_1 --shelf=$ANNEX_HASH_2'
|
|
# git config annex.cuneiform-retrieve-hook 'librarian --get --floor=$ANNEX_HASH_1 --shelf=$ANNEX_HASH_2 --title="$ANNEX_KEY" | tablet-reader --implement=coffee --implement=glasses --force-monastic-dedication | fromcuneiform > "$ANNEX_FILE"'
|
|
# git config annex.cuneiform-remove-hook 'librarian --get --floor=$ANNEX_HASH_1 --shelf=$ANNEX_HASH_2 --title="$ANNEX_KEY" | goon --hit-with-hammer'
|
|
# git config annex.cuneiform-checkpresent-hook 'librarian --find --force-distrust-catalog --floor=$ANNEX_HASH_1 --shelf=$ANNEX_HASH_2 --title="$ANNEX_KEY" --shout-title'
|
|
# git annex initremote library type=hook hooktype=cuneiform encryption=none
|
|
# git annex describe library "the reborn Library of Alexandria (upgrade to bronze plates pending)"
|
|
|
|
Can you spot the potential data loss bugs in the above simple example?
|
|
(Hint: What happens when the `tablet-proofreader` exits nonzero?)
|
|
|
|
## configuration
|
|
|
|
These parameters can be passed to `git annex initremote`:
|
|
|
|
* `hooktype` - Required. This specifies a collection of hooks to use for
|
|
this remote.
|
|
|
|
* `encryption` - One of "none", "hybrid", "shared", or "pubkey".
|
|
See [[encryption]].
|
|
|
|
* `keyid` - Specifies the gpg key to use for [[encryption]].
|
|
|
|
* `chunk` - Enables [[chunking]] when storing large files.
|
|
|
|
## hooks
|
|
|
|
Each type of hook remote is specified by a collection of hook commands.
|
|
Each hook command is run as a shell command line, and should return nonzero
|
|
on failure, and zero on success.
|
|
|
|
These environment variables are used to communicate with the hook commands:
|
|
|
|
* `ANNEX_KEY` - name of a key to store, retrieve, remove, or check.
|
|
* `ANNEX_FILE` - a file containing the key's content
|
|
* `ANNEX_HASH_1` - short stable value, based on the key, can be used for hashing
|
|
into 1024 buckets.
|
|
* `ANNEX_HASH_2` - another hash value, can be used for a second level of hashing
|
|
|
|
The settings to use in git config for the hook commands are as follows:
|
|
|
|
* `annex.$hooktype-store-hook` - Command run to store a key in the special remote.
|
|
`ANNEX_FILE` contains the content to be stored.
|
|
|
|
* `annex.$hooktype-retrieve-hook` - Command run to retrieve a key from the special remote.
|
|
`ANNEX_FILE` is a file that the retrieved content should be written to.
|
|
The file may already exist with a partial
|
|
copy of the content (or possibly just garbage), to allow for resuming
|
|
of partial transfers.
|
|
|
|
* `annex.$hooktype-remove-hook` - Command to remove a key from the special remote.
|
|
|
|
* `annex.$hooktype-checkpresent-hook` - Command to check if a key is present
|
|
in the special remote. Should output the key name to stdout, on its own line,
|
|
if and only if the key has been actively verified to be present in the
|
|
special remote (caching presence information is a very bad idea);
|
|
all other output to stdout will be ignored.
|
|
|
|
## combined hook program
|
|
|
|
Rather than setting all of the above hooks, you can write a single
|
|
program that handles everything, and set a single hook to make it be used.
|
|
|
|
# git config annex.demo-hook /usr/local/bin/annexdemo
|
|
# git annex initremote mydemorepo type=hook hooktype=demo encryption=none
|
|
|
|
But, doing that is deprecated -- it's better, and not much harder,
|
|
to write an [[external_special_remote|external]]!
|
|
|
|
If you still want to do this, the program just needs to look at the
|
|
`ANNEX_ACTION` environment variable to see what it's being asked to do.
|
|
For example:
|
|
|
|
[[!format sh """
|
|
#!/bin/sh
|
|
set -e
|
|
case "$ANNEX_ACTION" in
|
|
store)
|
|
demo-upload "$ANNEX_HASH_1/$ANNEX_HASH_2/$ANNEX_KEY" < "$ANNEX_FILE"
|
|
;;
|
|
retrieve)
|
|
demo-download "$ANNEX_HASH_1/$ANNEX_HASH_2/$ANNEX_KEY" > "$ANNEX_FILE"
|
|
;;
|
|
remove)
|
|
demo-nuke "$ANNEX_HASH_1/$ANNEX_HASH_2/$ANNEX_KEY"
|
|
;;
|
|
checkpresent)
|
|
if demo-exists "$ANNEX_HASH_1/$ANNEX_HASH_2/$ANNEX_KEY"; then
|
|
echo "$ANNEX_KEY"
|
|
fi
|
|
;;
|
|
*)
|
|
echo "unknown ANNEX_ACTION: $ANNEX_ACTION" >&2
|
|
exit 1
|
|
;;
|
|
esac
|
|
"""]]
|