How to set the default Docker data directory

1 minute read

Storage photo by Benjamin Lehman

If you’ve been using Docker for a while you’ve already seen its appetite for storage. All the images, layers, containers, etc. are stored on its default data directory /var/lib/docker:

/var/lib/docker/
├── buildkit
├── containers
├── image
├── network
├── nuke-graph-directory.sh
├── overlay2
├── plugins
├── runtimes
├── swarm
├── tmp
├── trust
└── volumes

As you keep building your images, running your containers and mounting your application’s volumes all those folders grow and grow and, since they are on the root partition /, it is quite easy to run out of space an ruin your system.

This post shows how to move and configure the Docker data directory. Docker recommends to use fast drives, as SSD, to store this data, but it can be actually installed on other types of hard drives.

Since it is likely that you want to keep your current volumes, images, etc. first we need to copy the default data directory /var/lib/docker to the new location; to do so we need to stop de Docker Daemon:

sudo service docker stop    # Assuming we are on a Linux machine

After that, we need to configure the Docker Daemon to use the new location by editing its configuration file located in /etc/docker/daemon.json and by adding the data-root property. Here [1] you can se a full configuration file with all its possible parameters:

{
    "data-root": "/path/to/your/data/docker"
}

Now let’s copy the current Docker data folder:


sudo rsync -aP /var/lib/docker/ /path/to/your/data/docker

Finally, let’s restart the Docker Daemon:

sudo service docker start

To check if Docker is using the new configuration, just execute:

docker info

And look for the “Docker Root Dir: «path»” entry.

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