title: How to execute Docker container as root
body: <p>when I connect to the graph-tool container in Docker, I can only enter it as user other than root. And if I use <code>docker exec -it --user root graph-tool bash</code>, it always show the following information:
  <code>OCI runtime exec failed: exec failed: container_linux.go:344: starting container process caused "chdir to cwd (\"/home/user\") set in config.json failed: permission denied": unknown</code></p>
  
  <p>could anybody tell me how to address it?</p>