Docker deamon config path under mac os

Docker 19+

Config file is now available in ~/.docker/daemon.json (see Ed's Answer)

Docker EE/CE 17+

Docker for Mac/Windows has added a config editor to the tray icon UI to allow editing of Dockers daemon.json file that will be persisted in the VM.

To access it go to the Docker Icon > Preferences > Daemon > Advanced

Original Answer

The Docker for Mac VM is based on Alpine Linux. The init system is based on OpenRC.

You can attach a screen session to the VM's tty (terminal) and poke around

$ screen ~/Library/Containers/com.docker.docker/Data/com.docker.driver.amd64-linux/tty

The docker daemon config is in the usual spot

moby:/etc/docker# ls -l /etc/docker/
total 8
-rw-r--r--    1 root     root            38 Aug  5 11:26 daemon.json
-rw-------    1 root     root           244 Aug  5 11:26 key.json

The /etc/init.d/docker script that manages the startup does not seem very configurable, apart from editing the script.

/host_docker_app in the VM is a mount of the data in ~/Library/Containers/com.docker.docker/Data/ from OSX. This seems like the most likely place to persist custom config but it doesn't look like there is any interface to source/load config or anything at startup from there.

It looks like changes outside of /var or /host_docker_app will not persist over reboots. There was a mechanism to persist some startup config in the old boot2docker VM image but I haven't found anything like it for the new VM.

On recent versions of Docker Desktop for Mac, the files are in ~/.docker.

~/.docker/daemon.json

Custom (ie. self-signed) certificates can be copied into

~/.docker/certs.d/{MyRegistry:port}/client.crt

I am using Docker for Mac 1.13.0 on MacOS 10.12 and the daemon settings can be accessed via the Docker app (Preferences -> Daemon -> Advanced).

But if you change this to something wrong, you will render your installation unusable (the daemon will no longer start-up). This happened to me.

I found out that the settings are stored in a Git repository in ~/Library/Containers/com.docker.docker/Data/database where I had to issue a git reset --hard HEAD before I could change anything. After that the daemon settings are available in ~/Library/Containers/com.docker.docker/Data/database/com.docker.driver.amd64-linux/etc/docker/daemon.json.

Edit, commit and restart the Docker app … et voilà … the daemon starts again.