# Docker Engine managed plugin system This document describes the plugin system available today in the **experimental build** of Docker 1.12: * [How to operate an existing plugin](#how-to-operate-a-plugin) * [How to develop a plugin](#how-to-develop-a-plugin) Unlike the legacy plugin system, you now manage plugins using Docker Engine: * install plugins * start plugins * stop plugins * remove plugins The current Docker Engine plugin system only supports volume drivers. We are adding more plugin driver types in the future releases. For information on Docker Engine plugins generally available in Docker Engine 1.12 and earlier, refer to [Understand legacy Docker Engine plugins](legacy_plugins.md). ## How to operate a plugin Plugins are distributed as Docker images, so develpers can host them on Docker Hub or on a private registry. You install the plugin using a single command: `docker plugin install `. The `plugin install` command pulls the plugin from the Docker Hub or private registry. If necessary the CLI prompts you to accept any privilige requriements. For example the plugin may require access to a device on the host system. Finally it enables the plugin. Run `docker plugin ls` to check the status of installed plugins. The Engine markes plugins that are started without issues as `ENABLED`. After you install a plugin, the plugin behavior is the same as legacy plugins. The following example demonstrates how to install the `sshfs` plugin and use it to create a volume. 1. Install the `sshfs` plugin. ```bash $ docker plugin install vieux/sshfs Plugin "vieux/sshfs" is requesting the following privileges: - network: [host] - capabilities: [CAP_SYS_ADMIN] Do you grant the above permissions? [y/N] y vieux/sshfs ``` The plugin requests 2 privileges, the `CAP_SYS_ADMIN` capability to be able to do mount inside the plugin and `host networking`. 2. Check for a value of `true` the `ENABLED` column to verify the plugin started without error. ```bash $ docker plugin ls NAME TAG ENABLED vieux/sshfs latest true ``` 3. Create a volume using the plugin. ```bash $ docker volume create \ -d vieux/sshfs \ --name sshvolume \ -o sshcmd=user@1.2.3.4:/remote sshvolume ``` 4. Use the volume `sshvolume`. ```bash $ docker run -v sshvolume:/data busybox ls /data ``` 5. Verify the plugin successfully created the volume. ```bash $ docker volume ls DRIVER NAME vieux/sshfs sshvolume ``` You can stop a plugin with the `docker plugin disable` command or remove a plugin with `docker plugin remove`. See the [command line reference](../reference/commandline/index.md) for more information. ## How to develop a plugin Plugin creation is currently a manual process. We plan to add automation in a future release with a command such as `docker plugin build`. This section describes the format of an existing enabled plugin. You have to create and format the plugin files by hand. Plugins are stored in `/var/lib/docker/plugins`. For instance: ```bash # ls -la /var/lib/docker/plugins total 20 drwx------ 4 root root 4096 Aug 8 18:03 . drwx--x--x 12 root root 4096 Aug 8 17:53 .. drwxr-xr-x 3 root root 4096 Aug 8 17:56 cd851ce43a403 -rw------- 1 root root 2107 Aug 8 18:03 plugins.json ``` `plugins.json` is an inventory of all installed plugins. For example: ```bash # cat plugins.json { "cd851ce43a403": { "plugin": { "Manifest": { "Args": { "Value": null, "Settable": null, "Description": "", "Name": "" }, "Env": null, "Devices": null, "Mounts": null, "Capabilities": [ "CAP_SYS_ADMIN" ], "ManifestVersion": "v0.1", "Description": "sshFS plugin for Docker", "Documentation": "https://docs.docker.com/engine/extend/plugins/", "Interface": { "Socket": "sshfs.sock", "Types": [ "docker.volumedriver/1.0" ] }, "Entrypoint": [ "/go/bin/docker-volume-sshfs" ], "Workdir": "", "User": {}, "Network": { "Type": "host" } }, "Config": { "Devices": null, "Args": null, "Env": [], "Mounts": [] }, "Active": true, "Tag": "latest", "Name": "vieux/sshfs", "Id": "cd851ce43a403" } } } ``` Each folder represents a plugin. For example: ```bash # ls -la /var/lib/docker/plugins/cd851ce43a403 total 12 drwx------ 19 root root 4096 Aug 8 17:56 rootfs -rw-r--r-- 1 root root 50 Aug 8 17:56 plugin-config.json -rw------- 1 root root 347 Aug 8 17:56 manifest.json ``` `rootfs` represents the root filesystem of the plugin. In this example, it was created from a Dockerfile as follows: >**Note:** `/run/docker/plugins` is mandatory for docker to communicate with the plugin._ ```bash $ git clone https://github.com/vieux/docker-volume-sshfs $ cd docker-volume-sshfs $ docker build -t rootfs . $ id=$(docker create rootfs true) # id was cd851ce43a403 when the image was created $ mkdir -p /var/lib/docker/plugins/$id/rootfs $ docker export "$id" | tar -x -C /var/lib/docker/plugins/$id/rootfs $ docker rm -vf "$id" $ docker rmi rootfs ``` `manifest.json` describes the plugin and `plugin-config.json` contains some runtime parameters. For example: ```bash # cat manifest.json { "manifestVersion": "v0.1", "description": "sshFS plugin for Docker", "documentation": "https://docs.docker.com/engine/extend/plugins/", "entrypoint": ["/go/bin/docker-volume-sshfs"], "network": { "type": "host" }, "interface" : { "types": ["docker.volumedriver/1.0"], "socket": "sshfs.sock" }, "capabilities": ["CAP_SYS_ADMIN"] } ``` In this example, you can see the plugin is a volume driver, requires the `CAP_SYS_ADMIN` capability, `host networking`, `/go/bin/docker-volume-sshfs` as entrypoint and is going to use `/run/docker/plugins/sshfs.sock` to communicate with the Docker Engine. ```bash # cat plugin-config.json { "Devices": null, "Args": null, "Env": [], "Mounts": [] } ``` This plugin doesn't require runtime parameters. Both `manifest.json` and `plugin-config.json` are part of the `plugins.json`. `manifest.json` is read-only and `plugin-config.json` is read-write. To summarize, follow the steps below to create a plugin: 0. Choose a name for the plugin. Plugin name uses the same format as images, for example: `/`. 1. Create a rootfs in `/var/lib/docker/plugins/$id/rootfs`. 2. Create manifest.json file in `/var/lib/docker/plugins/$id/`. 3. Create a `plugin-config.json` if needed. 4. Create or add a section to `/var/lib/docker/plugins/plugins.json`. Use `/` as “Name” and `$id` as “Id”. 5. Restart the Docker Engine. 6. Run `docker plugin ls`. * If your plugin is listed as `ENABLED=true`, you can push it to the registry. * If the plugin is not listed or if `ENABLED=false`, something went wrong. Check the daemon logs for errors. 7. If you are not already logged in, use `docker login` to authenticate against a registry. 8. Run `docker plugin push /` to push the plugin.