docs: add note to volume-plugins
The /var/lib/docker directory is reserved for
docker, and should not be touched by plugins.
@@ -15,7 +15,7 @@ storage systems, such as Amazon EBS, and enable data volumes to persist beyond
the lifetime of a single Docker host. See the [plugin documentation](plugins.md)
for more information.
-# Command-line changes
+## Command-line changes
A volume plugin makes use of the `-v`and `--volume-driver` flag on the `docker run` command. The `-v` flag accepts a volume name and the `--volume-driver` flag a driver type, for example:
@@ -32,13 +32,13 @@ server to another.
By specifying a `volumedriver` in conjunction with a `volumename`, users can use plugins such as [Flocker](https://clusterhq.com/docker-plugin/) to manage volumes external to a single host, such as those on EBS.
-# Create a VolumeDriver
+## Create a VolumeDriver
The container creation endpoint (`/containers/create`) accepts a `VolumeDriver`
field of type `string` allowing to specify the name of the driver. It's default
value of `"local"` (the default driver for local volumes).
-# Volume plugin protocol
+## Volume plugin protocol
If a plugin registers itself as a `VolumeDriver` when activated, then it is
expected to provide writeable paths on the host filesystem for the Docker
@@ -47,6 +47,10 @@ daemon to provide to containers to consume.
The Docker daemon handles bind-mounting the provided paths into user
containers.
+> **Note**: Volume plugins should *not* write data to the `/var/lib/docker/`
+> directory, including `/var/lib/docker/volumes`. The `/var/lib/docker/`
+> directory is reserved for Docker.
+
### /VolumeDriver.Create
**Request**:
