How to change the docker image installation direct

Question

From what I can tell, docker images are installed to /var/lib/docker as they are pulled. Is there a way to change this location, such as to a mounted volume like /mnt?

Answer 1

Since I haven't found the correct instructions for doing this in Fedora (EDIT: people pointed in comments that this should also work on CentOS and Suse) (/etc/default/docker isn't used there), I'm adding my answer here:

You have to edit /etc/sysconfig/docker, and add the -g option in the OPTIONS variable. If there's more than one option, make sure you enclose them in "". In my case, that file contained:

OPTIONS=--selinux-enabled

so it would become

OPTIONS="--selinux-enabled -g /mnt"

After a restart (systemctl restart docker) , Docker should use the new directory

Answer 2

As recommneded by @mbarthelemy this can be done via the -g option when starting the docker daemon directly.

However, if docker is being started as a system service, it is not recommended to modify the /etc/default/docker file. There is a guideline to this located here.

The correct approach is to create an /etc/docker/daemon.json file on Linux (or Mac) systems or %programdata%\docker\config\daemon.json on Windows. If this file is not being used for anything else, the following fields should suffice:

{
    "graph": "/docker/daemon_files"
}

This is assuming the new location where you want to have docker persist its data is /docker/daemon_files

Answer 3

On Fedora 26 and probably many other versions, you may encounter an error after moving your base folder location as described above. This is particularly true if you are moving it to somewhere under /home. This is because SeLinux kicks in and prevents the docker container from running many of its programs from under this location.

The short solution is to remove the --enable-selinux option when you add the -g parameter.

Answer 4

Following advice from comments I utilize Docker systemd documentation to improve this answer. Below procedure doesn't require reboot and is much cleaner.

First create directory and file for custom configuration:

sudo mkdir -p /etc/systemd/system/docker.service.d
sudo $EDITOR /etc/systemd/system/docker.service.d/docker-storage.conf

For docker version before 17.06-ce paste:

[Service]
ExecStart=
ExecStart=/usr/bin/docker daemon -H fd:// --graph="/mnt"

For docker after 17.06-ce paste:

[Service]
ExecStart=
ExecStart=/usr/bin/dockerd -H fd:// --data-root="/mnt"

Alternative method through daemon.json

I recently tried above procedure with 17.09-ce on Fedora 25 and it seem to not work. Instead of that simple modification in /etc/docker/daemon.json do the trick:

{
    "graph": "/mnt",
    "storage-driver": "overlay"
}

Despite the method you have to reload configuration and restart Docker:

sudo systemctl daemon-reload
sudo systemctl restart docker

To confirm that Docker was reconfigured:

docker info|grep "loop file"

In recent version (17.03) different command is required:

docker info|grep "Docker Root Dir"

Output should look like this:

 Data loop file: /mnt/devicemapper/devicemapper/data
 Metadata loop file: /mnt/devicemapper/devicemapper/metadata

Or:

 Docker Root Dir: /mnt

Then you can safely remove old Docker storage:

rm -rf /var/lib/docker

Answer 5

Much easier way to do so:

Stop docker service

sudo systemctl stop docker

Move existing docker directory to new location

sudo mv /var/lib/docker/ /path/to/new/docker/

Create symbolic link

sudo ln -s /path/to/new/docker/ /var/lib/docker/

Start docker service

sudo systemctl start docker

Answer 6

Don't use a symbolic Link to move the docker folder to /mnt (for example). This may cause in trouble with the docker rm command.

Better use the -g Option for docker. On Ubuntu you can set it permanently in /etc/default/docker.io. Enhance or replace the DOCKER_OPTS Line.

Here an example: `DOCKER_OPTS="-g /mnt/somewhere/else/docker/"