I have installed the docker daemon on a Debian 8 machine. And after setting a value for "DOCKER_OPTS" within the file "/etc/default/docker" I wanted to check if after restarting the service the value was set properly.
Is there a command to display the current docker's configuration ?
After some researches I found the following issue https://github.com/docker/docker/issues/9889 which explains that systemd ignores the configuration file /etc/default/docker. Therefore in my case "DOCKER_OPTS" is not set.
After editing the file /lib/systemd/system/docker.service it is possible to check that the value is set correctly with the command, mentioned by Adrian, ps aux | grep docker.
The other useful commands to check the installation version and system information are docker version and docker info.