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Docker - Enable Docker Remote API

Docker also provides a nice remote REST API.

Edit /etc/default/docker and update the DOCKER_OPTS variable to the following:

DOCKER_OPTS='-H tcp://0.0.0.0:1234 -H unix:///var/run/docker.sock'

NOTE: On non-Ubuntu machines, the docker config may be in an alternative location.

Instead of /etc/default/docker, try /etc/init/docker.conf

If running systemd docker daemon the /etc/default/docker is no longer effective. Instead you need to create a systemd dropin file:

Place a file under: /etc/systemd/system/docker.service.d/remote-api.conf

With the contents:

[Service]
ExecStart=
ExecStart=/usr/bin/dockerd -H tcp://127.0.0.1:1234 -H unix:///var/run/docker.sock

NOTE: The double ExecStart is necessary!

It also recommends binding on 127.0.0.1 instead of 0.0.0.0, unless you have a good reason!

This will have Docker bind to port 1234 which will be used by the Docker Remote API.

One you have saved your changes, you will need to restart the Docker process by running the following command:

sudo systemctl daemon-reload // reloading daemon definitions
sudo systemctl restart docker

To test that the Docker Remote API has been properly enabled, we will list the Images currently in Docker:

sudo docker images

Test by performing a GET operation on the following URL: http://172.30.0.199:1234/images/json as described in the Docker Remote API.

You can also easily test this by using CURL on the command-line by running the following command:

curl -X GET http://172.30.0.199:1234/images/json

References