docker login from Quay.io results in an odd error message
$ docker login https://quay.io/v1/ Username (username): 2014/01/01 12:00:00 Error: Invalid Registry endpoint: Get https://quay.io/v1/_ping: dial tcp: ping timeout
Docker has defined as maximum timeout of five seconds before a timeout will occur. Currently, the only solution is to find a connection with a better latency.
Note: This is probably fixed for Docker version 1.12.2 and greater.
There is a known issue with Vagrant whereby networking connections can sometimes become extremely slow. A solution can be found here.
If you are using docker on OSX via boot2docker, the networking stack can sometimes get out of sync. To fix it, restart the boot2docker image:
$ boot2docker restart
Docker-machine supersedes boot2docker on OSX. To fix weird state of docker, restart docker-machine:
$ docker-machine restart default