pgrep docker | head -1
2657
ps -P 2657
PID PSR TTY STAT TIME COMMAND
2657 0 ? Sl 2:10 dockerd --data-root /var/lib/docker -H unix:// --
ps -P 2657 | grep [d]ockerd
2657 0 ? Sl 2:10 dockerd --data-root /var/lib/docker -H unix:// --label provider=virtualbox -H tcp://0.0.0.0:2376 --tlsverify --tlscacert=/var/lib/boot2docker/ca.pem --tlskey=/var/lib/boot2docker/server-key.pem --tlscert=/var/lib/boot2docker/server.pem --storage-driver overlay2 --pidfile /var/run/docker.pid