Docker daemon windows 7 : concurrent downloads

Question

I've installed the docker toolbox on my machine. Once I try to pull down some images from a repository with docker pull, several of them "timeout". The docker documentation recommends that I configure the docker daemon to configure the number of concurrent download sessions:

dockerd --max-concurrent-downloads 1

However, when I execute the above command, I get the following error:

Error starting daemon: This version of Windows does not support the docker daemon

If I run docker.exe daemon I get the following error:

`docker daemon` is not supported on Windows. Please run `dockerd` directly

Is there a different way I can limit the number of concurrent downloads with the docker toolbox?

Answer 1

Docker toolbox nests the docker daemon (dockerd) inside a virtual machine that you can modify using docker-machine ssh.

The typical installation of Docker toolbox uses the Oracle Virtualbox driver, which uses by default the boot2docker image.

According to the documentation of boot2docker, you can add extra arguments for the docker deamon (ie. dockerd) by modifying the /var/lib/boot2docker/profile file:

Docker daemon options

If you need to customize the options used to start the Docker daemon, you can do so by adding entries to the /var/lib/boot2docker/profile file on the persistent partition inside the Boot2Docker virtual machine. Then restart the daemon.

If you are using this configuration (virtualbox + boot2docker), then the following command line might help you. Execute it in your Window shell, it will add the dockerd argument --max-concurrent-downloads with the value 1 for you, in the machine called "default":

docker-machine ssh default "echo \"EXTRA_ARGS=\\\"\$EXTRA_ARGS --max-concurrent-downloads 1\\\"\" | sudo tee -a /var/lib/boot2docker/profile"

Do not forget to restart your machine with docker-machine restart default.

By doing so I was able to add any dockerd argument (mind the version of dockerd used by boot2docker though).