docker lvm plugin

Docker Volume Driver for lvm volumes

This plugin can be used to create lvm volumes of specified size, which can then be bind mounted into the container using docker run command.

Setup

1) git clone git@github.com:projectatomic/docker-lvm-plugin.git (You can also use HTTPS to clone: git clone https://github.com/projectatomic/docker-lvm-plugin.git)
2) cd docker-lvm-plugin
3) export GO111MODULE=on
4) make
5) sudo make install

Wanna try it out!? (Vagrant)

From the $root directory of the project.

$ vagrant up

Once the VM is up and running (vagrant global-status will list you all the vagrant VMs running on your system), you can ssh into the VM by running vagrant ssh docker-lvm-plugin-fedora33.

Screencast

Usage

1. Start the docker daemon before starting the docker-lvm-plugin daemon. You can start docker daemon using command:

sudo systemctl start docker

2. Once docker daemon is up and running, you can start docker-lvm-plugin daemon using command:

sudo systemctl start docker-lvm-plugin

NOTE: docker-lvm-plugin daemon is on-demand socket activated. Running docker volume ls command will automatically start the daemon.

3. Since logical volumes (lv's) are based on a volume group, it is the responsibility of the user (administrator) to provide a volume group name. You can choose an existing volume group name by listing volume groups on your system using vgs command OR create a new volume group using vgcreate command. e.g.

vgcreate vg0 /dev/hda

where /dev/hda is your partition or whole disk on which physical volumes were created.

4. Add this volume group name in the config file

/etc/docker/docker-lvm-plugin

5. The docker-lvm-plugin also supports the creation of thinly-provisioned volumes. To create a thinly-provisioned volume, a user (administrator) must first create a thin pool using the lvcreate command.

lvcreate -L 10G -T vg0/mythinpool

This will create a thinpool named mythinpool of size 10G under volume group vg0. NOTE: thinpools are special kind of logical volumes carved out of the volume group. Hence in the above example, to create the thinpool mythinpool you must have atleast 10G of freespace in volume group vg0.

6. The docker-lvm-plugin allows you to create volumes using an optional volume group, which you can pass using --opt vg in docker volume create command. However, this is not recommended and user (administrator) should stick to the default volume group specified in /etc/docker/docker-lvm-plugin config file.

   If a user still chooses to create a volume using an optional volume group e.g --opt vg=vg1, user must pass --opt vg=vg1 when creating any derivative volumes based off this original volume. E.g

   • Any snapshot volumes which are created off a volume that was created using the optional volume group.
   • Any thin volumes which are created off a thin pool that was created using an optional volume group.

Volume Creation

docker volume create command supports the creation of regular lvm volumes, thin volumes, snapshots of regular and thin volumes.

Usage: docker volume create [OPTIONS]

-d, --driver    string    Specify volume driver name (default "local")
--label         list      Set metadata for a volume (default [])
--name          string    Specify volume name
-o, --opt       map       Set driver specific options (default map[])

Following options can be passed using -o or --opt

--opt size
--opt thinpool
--opt snapshot
--opt keyfile
--opt vg

Please see examples below on how to use these options.

Examples

$ docker volume create -d lvm --opt size=0.2G --name foobar

This will create a lvm volume named foobar of size 208 MB (0.2 GB) in the volume group vg0.

$ docker volume create -d lvm --opt size=0.2G --opt vg=vg1 --name foobar

This will create a lvm volume named foobar of size 208 MB (0.2 GB) in the volume group vg1.

docker volume create -d lvm --opt size=0.2G --opt thinpool=mythinpool --name thin_vol

This will create a thinly-provisioned lvm volume named thin_vol in mythinpool.

docker volume create -d lvm --opt snapshot=foobar --opt size=100M --name foobar_snapshot

This will create a snapshot volume of foobar named foobar_snapshot. For thin snapshots, use the same command above but don't specify a size.

docker volume create -d lvm --opt size=0.2G --opt keyfile=/root/key.bin --name crypt_vol

This will create a LUKS encrypted lvm volume named crypt_vol with the contents of /root/key.bin as a binary passphrase. Snapshots of encrypted volumes use the same key file. The key file must be present when the volume is created, and when it is mounted to a container.

Volume List

Use docker volume ls --help for more information.

$ docker volume ls

This will list volumes created by all docker drivers including the default driver (local).

Volume Inspect

Use docker volume inspect --help for more information.

$ docker volume inspect foobar

This will inspect foobar and return a JSON.

[
    {
        "Driver": "lvm",
        "Labels": {},
        "Mountpoint": "/var/lib/docker-lvm-plugin/foobar",
        "Name": "foobar",
        "Options": {
            "size": "0.2G"
        },
        "Scope": "local"
    }
]

Volume Removal

Use docker volume rm --help for more information.

$ docker volume rm foobar

This will remove lvm volume foobar.

Bind Mount lvm volume inside the container

$ docker run -it -v foobar:/home fedora /bin/bash

This will bind mount the logical volume foobar into the home directory of the container.

Tests

sudo make test

NOTE: These are destructive tests and can leave the system in a changed state.
It is highly recommended to run these tests either as part of a CI/CD system or on a immutable infrastructure e.g VMs.

Currently supported environments.

Fedora, RHEL, Centos, Ubuntu (>= 16.04)

License

GNU GPL