Debugging docker daemon Issues

There are a few actions that should be taken in the event that the docker daemon becomes unresponsive to cli commands. These will allow for further investigation of why the daemon is hanging. 

Dump Docker Stacktrace

Get the PID of dockerd:

$ pidof dockerd
1082

Send a sig event: 

$ sudo kill -10 1082
$ printf "$(sudo journalctl -u docker -o cat --lines=50)"

You can run an strace on the docker PID:

$ systemctl status docker.service | grep PID
 Main PID:  1023  (docker)

$ sudo strace -f -p 1023 -o docker-strace.log & 

The docker-strace.log should provide additional context.

Send these outputs along with any additional information that may be useful when submitting a ticket to support@coreos.com