mirror of https://github.com/docker/cli.git
273 lines
6.9 KiB
Markdown
273 lines
6.9 KiB
Markdown
---
|
|
title: "Volume plugins"
|
|
description: "How to manage data with external volume plugins"
|
|
keywords: ["Examples, Usage, volume, docker, data, volumes, plugin, api"]
|
|
---
|
|
|
|
<!-- This file is maintained within the docker/docker Github
|
|
repository at https://github.com/docker/docker/. Make all
|
|
pull requests against that repo. If you see this file in
|
|
another repository, consider it read-only there, as it will
|
|
periodically be overwritten by the definitive file. Pull
|
|
requests which include edits to this file in other repositories
|
|
will be rejected.
|
|
-->
|
|
|
|
# Write a volume plugin
|
|
|
|
Docker Engine volume plugins enable Engine deployments to be integrated with
|
|
external storage systems, such as Amazon EBS, and enable data volumes to persist
|
|
beyond the lifetime of a single Engine host. See the
|
|
[plugin documentation](legacy_plugins.md) for more information.
|
|
|
|
## Changelog
|
|
|
|
### 1.12.0
|
|
|
|
- Add `Status` field to `VolumeDriver.Get` response ([#21006](https://github.com/docker/docker/pull/21006#))
|
|
- Add `VolumeDriver.Capabilities` to get capabilities of the volume driver([#22077](https://github.com/docker/docker/pull/22077))
|
|
|
|
### 1.10.0
|
|
|
|
- Add `VolumeDriver.Get` which gets the details about the volume ([#16534](https://github.com/docker/docker/pull/16534))
|
|
- Add `VolumeDriver.List` which lists all volumes owned by the driver ([#16534](https://github.com/docker/docker/pull/16534))
|
|
|
|
### 1.8.0
|
|
|
|
- Initial support for volume driver plugins ([#14659](https://github.com/docker/docker/pull/14659))
|
|
|
|
## 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:
|
|
|
|
$ docker run -ti -v volumename:/data --volume-driver=flocker busybox sh
|
|
|
|
This command passes the `volumename` through to the volume plugin as a
|
|
user-given name for the volume. The `volumename` must not begin with a `/`.
|
|
|
|
By having the user specify a `volumename`, a plugin can associate the volume
|
|
with an external volume beyond the lifetime of a single container or container
|
|
host. This can be used, for example, to move a stateful container from one
|
|
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
|
|
|
|
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
|
|
|
|
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
|
|
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**:
|
|
```json
|
|
{
|
|
"Name": "volume_name",
|
|
"Opts": {}
|
|
}
|
|
```
|
|
|
|
Instruct the plugin that the user wants to create a volume, given a user
|
|
specified volume name. The plugin does not need to actually manifest the
|
|
volume on the filesystem yet (until Mount is called).
|
|
Opts is a map of driver specific options passed through from the user request.
|
|
|
|
**Response**:
|
|
```json
|
|
{
|
|
"Err": ""
|
|
}
|
|
```
|
|
|
|
Respond with a string error if an error occurred.
|
|
|
|
### /VolumeDriver.Remove
|
|
|
|
**Request**:
|
|
```json
|
|
{
|
|
"Name": "volume_name"
|
|
}
|
|
```
|
|
|
|
Delete the specified volume from disk. This request is issued when a user invokes `docker rm -v` to remove volumes associated with a container.
|
|
|
|
**Response**:
|
|
```json
|
|
{
|
|
"Err": ""
|
|
}
|
|
```
|
|
|
|
Respond with a string error if an error occurred.
|
|
|
|
### /VolumeDriver.Mount
|
|
|
|
**Request**:
|
|
```json
|
|
{
|
|
"Name": "volume_name",
|
|
"ID": "b87d7442095999a92b65b3d9691e697b61713829cc0ffd1bb72e4ccd51aa4d6c"
|
|
}
|
|
```
|
|
|
|
Docker requires the plugin to provide a volume, given a user specified volume
|
|
name. This is called once per container start. If the same volume_name is requested
|
|
more than once, the plugin may need to keep track of each new mount request and provision
|
|
at the first mount request and deprovision at the last corresponding unmount request.
|
|
|
|
`ID` is a unique ID for the caller that is requesting the mount.
|
|
|
|
**Response**:
|
|
```json
|
|
{
|
|
"Mountpoint": "/path/to/directory/on/host",
|
|
"Err": ""
|
|
}
|
|
```
|
|
|
|
Respond with the path on the host filesystem where the volume has been made
|
|
available, and/or a string error if an error occurred.
|
|
|
|
### /VolumeDriver.Path
|
|
|
|
**Request**:
|
|
```json
|
|
{
|
|
"Name": "volume_name"
|
|
}
|
|
```
|
|
|
|
Docker needs reminding of the path to the volume on the host.
|
|
|
|
**Response**:
|
|
```json
|
|
{
|
|
"Mountpoint": "/path/to/directory/on/host",
|
|
"Err": ""
|
|
}
|
|
```
|
|
|
|
Respond with the path on the host filesystem where the volume has been made
|
|
available, and/or a string error if an error occurred. `Mountpoint` is optional,
|
|
however the plugin may be queried again later if one is not provided.
|
|
|
|
### /VolumeDriver.Unmount
|
|
|
|
**Request**:
|
|
```json
|
|
{
|
|
"Name": "volume_name",
|
|
"ID": "b87d7442095999a92b65b3d9691e697b61713829cc0ffd1bb72e4ccd51aa4d6c"
|
|
}
|
|
```
|
|
|
|
Indication that Docker no longer is using the named volume. This is called once
|
|
per container stop. Plugin may deduce that it is safe to deprovision it at
|
|
this point.
|
|
|
|
`ID` is a unique ID for the caller that is requesting the mount.
|
|
|
|
**Response**:
|
|
```json
|
|
{
|
|
"Err": ""
|
|
}
|
|
```
|
|
|
|
Respond with a string error if an error occurred.
|
|
|
|
|
|
### /VolumeDriver.Get
|
|
|
|
**Request**:
|
|
```json
|
|
{
|
|
"Name": "volume_name"
|
|
}
|
|
```
|
|
|
|
Get the volume info.
|
|
|
|
|
|
**Response**:
|
|
```json
|
|
{
|
|
"Volume": {
|
|
"Name": "volume_name",
|
|
"Mountpoint": "/path/to/directory/on/host",
|
|
"Status": {}
|
|
},
|
|
"Err": ""
|
|
}
|
|
```
|
|
|
|
Respond with a string error if an error occurred. `Mountpoint` and `Status` are
|
|
optional.
|
|
|
|
|
|
### /VolumeDriver.List
|
|
|
|
**Request**:
|
|
```json
|
|
{}
|
|
```
|
|
|
|
Get the list of volumes registered with the plugin.
|
|
|
|
**Response**:
|
|
```json
|
|
{
|
|
"Volumes": [
|
|
{
|
|
"Name": "volume_name",
|
|
"Mountpoint": "/path/to/directory/on/host"
|
|
}
|
|
],
|
|
"Err": ""
|
|
}
|
|
```
|
|
|
|
Respond with a string error if an error occurred. `Mountpoint` is optional.
|
|
|
|
### /VolumeDriver.Capabilities
|
|
|
|
**Request**:
|
|
```json
|
|
{}
|
|
```
|
|
|
|
Get the list of capabilities the driver supports.
|
|
The driver is not required to implement this endpoint, however in such cases
|
|
the default values will be taken.
|
|
|
|
**Response**:
|
|
```json
|
|
{
|
|
"Capabilities": {
|
|
"Scope": "global"
|
|
}
|
|
}
|
|
```
|
|
|
|
Supported scopes are `global` and `local`. Any other value in `Scope` will be
|
|
ignored and assumed to be `local`. Scope allows cluster managers to handle the
|
|
volume differently, for instance with a scope of `global`, the cluster manager
|
|
knows it only needs to create the volume once instead of on every engine. More
|
|
capabilities may be added in the future.
|