Today i was stumbling upon ZFS in Docker Docs.
The ZFS on Linux (ZoL) port is healthy and maturing. However, at this point in time it is not recommended to use the zfs Docker storage driver for production use unless you have substantial experience with ZFS on Linux.
I do have, so let’s try things out. I’m not installting any Ubuntu ZFS thingy, just grabbed one of my lab Proxmox installations with ZFS builtin. In this test, there was no running Docker daemon before the next steps. If you already are running Docker, you should stop the service, rename (or delete) /var/lib/docker and continue.
Create a dataset for Docker
zfs create -o mountpoint=/var/lib/docker -p rpool/data/docker
I’m using the default rpool, as this is just a test setup. For production use, you might think about another dedicated zpool.
Configure Docker to use ZFS
Add to /etc/docker/daemon.json:
{
"storage-driver": "zfs"
}
Adjust to your needs.
Start Docker and check storage driver
root@lab:~# docker info
Containers: 0
Running: 0
Paused: 0
Stopped: 0
Images: 1
Server Version: 1.12.3
Storage Driver: zfs
Zpool: rpool
Zpool Health: ONLINE
Parent Dataset: rpool/data/docker
Space Used By Parent: 98304
Space Available: 82527678464
Parent Quota: no
Compression: lz4
...
Pull an image and check ZFS
root@lab:~# docker pull ubuntu:xenial
xenial: Pulling from library/ubuntu
aed15891ba52: Pull complete
773ae8583d14: Pull complete
d1d48771f782: Pull complete
cd3d6cd6c0cf: Pull complete
8ff6f8a9120c: Pull complete
Digest: sha256:35bc48a1ca97c3971611dc4662d08d131869daa692acb281c7e9e052924e38b1
Status: Downloaded newer image for ubuntu:xenial
root@lab:~# zfs list -r rpool/data/docker
NAME USED AVAIL REFER MOUNTPOINT
rpool/data/docker 90.4M 76.7G 852K /var/lib/docker
rpool/data/docker/03cbcae48dd4a769bd9709791710f22f6ae594a4e6210fd06cf4a689e1db3f4c 112K 76.7G 83.1M legacy
rpool/data/docker/2e06fa8a3967dff7453fda15fdfdcaf60189bf91a372b782c002a9341c6dae2c 160K 76.7G 83.1M legacy
rpool/data/docker/38207bb42aebd11dee6a3883263f8c29fb21817d90de0ad7e5db9360dc6a5729 228K 76.7G 88.9M legacy
rpool/data/docker/c20becbd3210cd4884ccf89561f0f8d05fb2fc1e4e1d2881f9de321cc9153f41 132K 76.7G 83.1M legacy
rpool/data/docker/f9c1b3b86b5a8fed9be094874fd8b759cdad095b64b7680162cdeb2bcdcddc48 88.9M 76.7G 88.9M legacy
As you can see, each single layers gets an own dataset.
Run a container, do something, check ZFS
root@lab:~# docker run -it ubuntu:xenial /bin/bash
# ... do something inside container and exit
root@lab:~# zfs list -r rpool/data/docker
NAME USED AVAIL REFER MOUNTPOINT
rpool/data/docker 399M 76.5G 952K /var/lib/docker
rpool/data/docker/03cbcae48dd4a769bd9709791710f22f6ae594a4e6210fd06cf4a689e1db3f4c 112K 76.5G 83.1M legacy
rpool/data/docker/2e06fa8a3967dff7453fda15fdfdcaf60189bf91a372b782c002a9341c6dae2c 160K 76.5G 83.1M legacy
rpool/data/docker/38207bb42aebd11dee6a3883263f8c29fb21817d90de0ad7e5db9360dc6a5729 228K 76.5G 88.9M legacy
rpool/data/docker/576a9aa247d01a90ec15ad397be9317bd910e20e3f8479c5190881662f82ff8e 308M 76.5G 383M legacy
rpool/data/docker/576a9aa247d01a90ec15ad397be9317bd910e20e3f8479c5190881662f82ff8e-init 152K 76.5G 83.1M legacy
rpool/data/docker/c20becbd3210cd4884ccf89561f0f8d05fb2fc1e4e1d2881f9de321cc9153f41 132K 76.5G 83.1M legacy
rpool/data/docker/f9c1b3b86b5a8fed9be094874fd8b759cdad095b64b7680162cdeb2bcdcddc48 88.9M 76.5G 88.9M legacy
Now you can see the container dataset 576a9aa247d01a90ec15ad397be9317bd910e20e3f8479c5190881662f82ff8e. If you remove the container instance, it will disappear.
Awesome!