Move the Docker data directory

Unless otherwise configured, the Docker daemon stores its data in the directory, /var/lib/docker. This post describes how to configure Docker to store its data in a different folder.

In my case, I have a 256 GB hard drive on my laptop, which dual boots to Linux or Windows. I mounted the Linux root directory to a 45 GB partition, the /home directory to a 90 GB partition, and 8 GB to a swap partition. The rest of the hard drive is used by Windows. I run Ubuntu and I found that 45 GB is a bit tight for the Ubuntu system because the snaps packages use up a lot of space. Adding large Docker images into the same partition was causing it to fill up. I decided to store Docker data in my home partition, where I have more space.

Configure the Docker daemon

The Docker documentation describes how to change the Docker data directory.

First, stop the Docker daemon:

$ sudo service docker stop

Then, create a new Docker daemon configuration file, if one does not already exist. If one does exist, edit the existing file:

$ sudo nano /etc/docker/daemon.json

Add the following configuration information to the file:

{
  "data-root": "/home/docker-data"
}

You may choose any name for the new directory. I chose /home/docker-data. Save the file.

Copy the Docker data directory

Next, create the new Docker data directory in your specified location and copy the existing docker data over to it while maintaining all existing permissions:

$ sudo rsync -aq /var/lib/docker/ /home/docker-data

Test the new directory

For testing purposes, rename the old docker data directory so it cannot be used by Docker:

$ sudo mv /var/lib/docker /var/lib/docker-old

Start the Docker daemon:

$ sudo service docker start

Test that Docker can access its data in the new directory. If you have some containers already created you should be able to list them and their images:

$ docker ps -a
CONTAINER ID   IMAGE             COMMAND                  CREATED       STATUS                   PORTS     NAMES
4fdf96abb044   postgres:alpine   "docker-entrypoint.s…"   5 weeks ago   Exited (0) 5 weeks ago             postgres_db
$ docker images
docker images
REPOSITORY                       TAG       IMAGE ID       CREATED        SIZE
postgres                         alpine    46d837b93a1c   2 months ago   239MB
redis                            latest    39ac5829bade   3 months ago   138MB
blinklet/user-mapping            v1        9ce0b76c0af7   3 months ago   113MB
postgres-chinook-image           latest    503246416dbf   3 months ago   414MB
blinklet/adventureworks          latest    ef97417e6827   3 months ago   3.08GB
python                           alpine    cecbd2a9585a   4 months ago   52MB

Delete the old data

After successfully testing Docker, free up disk space on the root partition by deleting the old Docker data directory:

$ sudo rm -rf /var/lib/docker-old

Conclusion

I showed how to configure Docker to store its data in a different directory.