Move docker volume to different partition - docker

Question

I have a server where I run some containers with volumes. All my volumes are in /var/lib/docker/volumes/ because docker is managing it. I use docker-compose to start my containers.
Recently, I tried to stop one of my container but it was impossible :
$ docker-compose down
[17849] INTERNAL ERROR: cannot create temporary directory!
So, I checked how the data is mounted on the server :
$ df -h
Filesystem Size Used Avail Use% Mounted on
udev 7,8G 0 7,8G 0% /dev
tmpfs 1,6G 1,9M 1,6G 1% /run
/dev/md3 20G 19G 0 100% /
tmpfs 7,9G 0 7,9G 0% /dev/shm
tmpfs 5,0M 0 5,0M 0% /run/lock
tmpfs 7,9G 0 7,9G 0% /sys/fs/cgroup
/dev/md2 487M 147M 311M 33% /boot
/dev/md4 1,8T 1,7G 1,7T 1% /home
tmpfs 1,6G 0 1,6G 0% /run/user/1000
As you can see, the / is only 20Go, so it is full and I can't stop my containers using docker-compose.
My questions are :
There is a simple solution to increase the available space in the
/, using /dev/md4 ?
Or can I move volumes to another place without losing data ?

Answer 1

This part of the Docker Daemon is confirgurable. Best practices would have you change the data folder; this can be done with OS-level Linux commands like a symlink... I would say it's better to actually configure the Docker Daemon to store the data elsewhere!
You can do that by editing the Docker command line (e.g. the systemd script that starts the Docker daemon), or change /etc/docker/daemon.json.
The file should have this content:
{
"data-root": "/path/to/your/docker"
}
If you add a new hard drive, partition, or mount point you can add it here and docker will store its data there.

Answer 2

I landed here as I had the very same issue. Even though some sources suggest you could do it with a symbolic link this will cause all kinds of issues.
Depending on the OS and Docker version I had malformed images, weird errors or the docker-daemon refused to start.
Here is a solution, but it seems it varies a little from version to version. For me the solution was:
Open
/lib/systemd/system/docker.service
And change this line
ExecStart=/usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock
to:
ExecStart=/usr/bin/dockerd -g /mnt/WHATEVERYOUR/PARTITIONIS/docker --containerd=/run/containerd/containerd.sock

Answer 3

I solved it creating a symbolic link to a partition with bigger size:
ln -s /scratch/docker_meta /var/lib/docker
/scratch/docker_meta is the folder that I have in a bigger partition.

Answer 4

Do a bind mount.
For example, moving /docker/volumes to /mnt/large.
Append line into /etc/fstab.
/mnt/large /docker/volumes none bind 0 0
And then.
mv /docker/volumes/* /mnt/large/
mount /docker/volumes
Do not forget chown and chmod of /mnt/large first, if you are using non-root docker.