Signed-off-by: Zhang Wei <zhangwei555@huawei.com>
7.5 KiB
title | description | keywords | advisory |
---|---|---|---|
Graphdriver plugins | How to manage image and container filesystems with external plugins | Examples, Usage, storage, image, docker, data, graph, plugin, api | experimental |
Changelog
1.13.0
- Support v2 plugins
Docker graph driver plugins
Docker graph driver plugins enable admins to use an external/out-of-process graph driver for use with Docker engine. This is an alternative to using the built-in storage drivers, such as aufs/overlay/devicemapper/btrfs.
You need to install and enable the plugin and then restart the Docker daemon before using the plugin. See the following example for the correct ordering of steps.
$ docker plugin install cpuguy83/docker-overlay2-graphdriver-plugin # this command also enables the driver
<output suppressed>
$ pkill dockerd
$ dockerd --experimental -s cpuguy83/docker-overlay2-graphdriver-plugin
Write a graph driver plugin
See the plugin documentation for detailed information on the underlying plugin protocol.
Graph Driver plugin protocol
If a plugin registers itself as a GraphDriver
when activated, then it is
expected to provide the rootfs for containers as well as image layer storage.
/GraphDriver.Init
Request:
{
"Home": "/graph/home/path",
"Opts": [],
"UIDMaps": [],
"GIDMaps": []
}
Initialize the graph driver plugin with a home directory and array of options. These are passed through from the user, but the plugin is not required to parse or honor them.
The request also includes a list of UID and GID mappings, structed as follows:
{
"ContainerID": 0,
"HostID": 0,
"Size": 0
}
Response:
{
"Err": ""
}
Respond with a non-empty string error if an error occurred.
/GraphDriver.Create
Request:
{
"ID": "46fe8644f2572fd1e505364f7581e0c9dbc7f14640bd1fb6ce97714fb6fc5187",
"Parent": "2cd9c322cb78a55e8212aa3ea8425a4180236d7106938ec921d0935a4b8ca142",
"MountLabel": "",
"StorageOpt": {}
}
Create a new, empty, read-only filesystem layer with the specified
ID
, Parent
and MountLabel
. If Parent
is an empty string, there is no
parent layer. StorageOpt
is map of strings which indicate storage options.
Response:
{
"Err": ""
}
Respond with a non-empty string error if an error occurred.
/GraphDriver.CreateReadWrite
Request:
{
"ID": "46fe8644f2572fd1e505364f7581e0c9dbc7f14640bd1fb6ce97714fb6fc5187",
"Parent": "2cd9c322cb78a55e8212aa3ea8425a4180236d7106938ec921d0935a4b8ca142",
"MountLabel": "",
"StorageOpt": {}
}
Similar to /GraphDriver.Create
but creates a read-write filesystem layer.
/GraphDriver.Remove
Request:
{
"ID": "46fe8644f2572fd1e505364f7581e0c9dbc7f14640bd1fb6ce97714fb6fc5187"
}
Remove the filesystem layer with this given ID
.
Response:
{
"Err": ""
}
Respond with a non-empty string error if an error occurred.
/GraphDriver.Get
Request:
{
"ID": "46fe8644f2572fd1e505364f7581e0c9dbc7f14640bd1fb6ce97714fb6fc5187",
"MountLabel": ""
}
Get the mountpoint for the layered filesystem referred to by the given ID
.
Response:
{
"Dir": "/var/mygraph/46fe8644f2572fd1e505364f7581e0c9dbc7f14640bd1fb6ce97714fb6fc5187",
"Err": ""
}
Respond with the absolute path to the mounted layered filesystem. Respond with a non-empty string error if an error occurred.
/GraphDriver.Put
Request:
{
"ID": "46fe8644f2572fd1e505364f7581e0c9dbc7f14640bd1fb6ce97714fb6fc5187"
}
Release the system resources for the specified ID
, such as unmounting the
filesystem layer.
Response:
{
"Err": ""
}
Respond with a non-empty string error if an error occurred.
/GraphDriver.Exists
Request:
{
"ID": "46fe8644f2572fd1e505364f7581e0c9dbc7f14640bd1fb6ce97714fb6fc5187"
}
Determine if a filesystem layer with the specified ID
exists.
Response:
{
"Exists": true
}
Respond with a boolean for whether or not the filesystem layer with the specified
ID
exists.
/GraphDriver.Status
Request:
{}
Get low-level diagnostic information about the graph driver.
Response:
{
"Status": [[]]
}
Respond with a 2-D array with key/value pairs for the underlying status information.
/GraphDriver.GetMetadata
Request:
{
"ID": "46fe8644f2572fd1e505364f7581e0c9dbc7f14640bd1fb6ce97714fb6fc5187"
}
Get low-level diagnostic information about the layered filesystem with the
with the specified ID
Response:
{
"Metadata": {},
"Err": ""
}
Respond with a set of key/value pairs containing the low-level diagnostic information about the layered filesystem. Respond with a non-empty string error if an error occurred.
/GraphDriver.Cleanup
Request:
{}
Perform necessary tasks to release resources help by the plugin, such as unmounting all the layered file systems.
Response:
{
"Err": ""
}
Respond with a non-empty string error if an error occurred.
/GraphDriver.Diff
Request:
{
"ID": "46fe8644f2572fd1e505364f7581e0c9dbc7f14640bd1fb6ce97714fb6fc5187",
"Parent": "2cd9c322cb78a55e8212aa3ea8425a4180236d7106938ec921d0935a4b8ca142"
}
Get an archive of the changes between the filesystem layers specified by the ID
and Parent
. Parent
may be an empty string, in which case there is no parent.
Response:
{{ TAR STREAM }}
/GraphDriver.Changes
Request:
{
"ID": "46fe8644f2572fd1e505364f7581e0c9dbc7f14640bd1fb6ce97714fb6fc5187",
"Parent": "2cd9c322cb78a55e8212aa3ea8425a4180236d7106938ec921d0935a4b8ca142"
}
Get a list of changes between the filesystem layers specified by the ID
and
Parent
. If Parent
is an empty string, there is no parent.
Response:
{
"Changes": [{}],
"Err": ""
}
Respond with a list of changes. The structure of a change is:
"Path": "/some/path",
"Kind": 0,
Where the Path
is the filesystem path within the layered filesystem that is
changed and Kind
is an integer specifying the type of change that occurred:
- 0 - Modified
- 1 - Added
- 2 - Deleted
Respond with a non-empty string error if an error occurred.
/GraphDriver.ApplyDiff
Request:
{{ TAR STREAM }}
Extract the changeset from the given diff into the layer with the specified ID
and Parent
Query Parameters:
- id (required)- the
ID
of the new filesystem layer to extract the diff to - parent (required)- the
Parent
of the givenID
Response:
{
"Size": 512366,
"Err": ""
}
Respond with the size of the new layer in bytes. Respond with a non-empty string error if an error occurred.
/GraphDriver.DiffSize
Request:
{
"ID": "46fe8644f2572fd1e505364f7581e0c9dbc7f14640bd1fb6ce97714fb6fc5187",
"Parent": "2cd9c322cb78a55e8212aa3ea8425a4180236d7106938ec921d0935a4b8ca142"
}
Calculate the changes between the specified ID
Response:
{
"Size": 512366,
"Err": ""
}
Respond with the size changes between the specified ID
and Parent
Respond with a non-empty string error if an error occurred.