How do I enable "debug" logging of the Docker daemon? (Ubuntu 16.04)

I want to set the verbosity level of the docker deamon in ubuntu 16.04)

Docker version = 1.12.6

The following didn't work:

• /etc/docker/daemon.json, setting"debug": true (can not find the file)
• docker -d (error docker flag provided but not defined deamon)

The recommended way when using systemd is drop-ins. See the documentation here. You can create the file at /etc/docker/daemon.json if it does not already exist.

Add the following code snippet:

{ "debug": true }

You will need to restart the docker service at that point sudo systemctl restart docker

EDIT:

Because you are using an older version of Docker, you may need to do things differently.

Run systemctl show --property=FragmentPath docker to show the default file. This should be something like /lib/systemd/system/docker.service

Edit this file and add EnvironmentFile=/etc/default/docker

Add the -D flag to DOCKER_OPTS in /etc/default/docker and restart the service.

Further docs for your particular version here