Docker listening on a port it shouldn't be (-H=tcp://

I have a node where I am trying to run a docker container that exposes port 4444. When the container starts, it says Bind for failed: port is already allocated.

So I stopped all docker containers (I even ended up deleting all docker images.) Did a docker image prune and docker system prune -a.

The problem is that on this Linux host only, Docker is listening on port 4444 which causes a problem.

$ ps aux | grep 4444
root 4006719 8.3 0.2 1230764 78924 ? Ssl 09:34 0:00 /usr/bin/dockerd -H fd:// -H=tcp://

Why does it listen on tcp:// ? I need that port for Selenium!

  • OS is Linux (Ubuntu 20.04 focal)
  • Docker version is Docker version 19.03.13, build 4484c46d9d
  • Steps to reproduce: We have had docker on this host for a while now so it is impossible to state all the history. The current steps are to simply run “ps aux | grep 4444” with or without restarting dockerd first.