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This command implements the Docker volume plugin API allowing docker to use rclone as a data storage mechanism for various cloud providers. rclone provides docker volume plugin based on it.
To create a docker plugin, one must create a Unix or TCP socket that Docker will look for when you use the plugin and then it listens for commands from docker daemon and runs the corresponding code when necessary. Docker plugins can run as a managed plugin under control of the docker daemon or as an independent native service. For testing, you can just run it directly from the command line, for example:
sudo rclone serve docker --base-dir /tmp/rclone-volumes --socket-addr localhost:8787 -vv
Running rclone serve docker will create the said socket, listening for
commands from Docker to create the necessary Volumes. Normally you need not
give the --socket-addr flag. The API will listen on the unix domain socket
at /run/docker/plugins/rclone.sock. In the example above rclone will create
a TCP socket and a small file /etc/docker/plugins/rclone.spec containing
the socket address. We use sudo because both paths are writeable only by
the root user.
If you later decide to change listening socket, the docker daemon must be
restarted to reconnect to /run/docker/plugins/rclone.sock
or parse new /etc/docker/plugins/rclone.spec. Until you restart, any
volume related docker commands will timeout trying to access the old socket.
Running directly is supported on Linux only, not on Windows or MacOS.
This is not a problem with managed plugin mode described in details
in the full documentation.
The command will create volume mounts under the path given by --base-dir
(by default /var/lib/docker-volumes/rclone available only to root)
and maintain the JSON formatted file docker-plugin.state in the rclone cache
directory with book-keeping records of created and mounted volumes.
All mount and VFS options are submitted by the docker daemon via API, but you can also provide defaults on the command line as well as set path to the config file and cache directory or adjust logging verbosity.