Network timed out while trying to connect to https://index.docker.io

The simpler solution is to add the following entry in /etc/default/docker file

export http_proxy="http://HOST:PORT/"

and restart the docker service

service docker restart

I installed Docker without the Toolbox on Windows 10, so the version that requires Hyper-V to be enabled.

For Docker version 1.12 I had to go into the taskbar, right click the Docker Icon, select Settings -> Network and set the DNS Server to fixed, so that is uses Google's DNS server at 8.8.8.8.

Once that setting was changed, it finally worked.

I had the same problem this morning and the following fixed it for me:

$ docker-machine restart default      # Restart the environment
$ eval $(docker-machine env default)  # Refresh your environment settings

It appears that this is due to the Docker virtual machine getting itself into a strange state. There is an open github issue here

Update August 2016

Using Docker for Mac (version 1.12.0), was seeing issues of the form:

➜  docker pull node
Using default tag: latest
Pulling repository docker.io/library/node
Network timed out while trying to connect to https://index.docker.io/v1/repositories/library/node/images. You may want to check your internet connection or if you are behind a proxy.`enter code here`

This was resolved by updating my MacBook Pro wireless network settings to include the following DNS entry: 8.8.8.8

For further info, please see this (dated) issue which provided the answer given here.