No se puede conectar al docker daemon

He intentado todo: agregar usuario, lo probé con sudo pero no lo solucioné.

Lo probé como: sudo docker ps y docker ps

Versión Docker: 1.11.2 OS / Archlinux

da un error: no se puede conectar al demonio Docker. ¿Se está ejecutando el Docker Daemon en este host?

systemctl status docker :
 ● docker.service - Docker Application Container Engine
Loaded: loaded (/usr/lib/systemd/system/docker.service;  enabled;   vendor preset: disabled)
Active: active (running) since Tue 2016-08-16 12:34:14 UTC; 13min ago
 Docs: https://docs.docker.com
Main PID: 2323 (docker)
Tasks: 21 (limit: 4915)
Memory: 24.2M
  CPU: 649ms
CGroup: /system.slice/docker.service
       ├─2323 /usr/bin/docker daemon -H fd://
       └─2339 docker-containerd -l /var/run/docker/libcontainerd /docker-containerd.sock --runtime docker-run
Aug 16 12:34:13 localhost docker[2323]: time="2016-08-16T12:34:13.730808484Z" level=info msg="[graphdriver] usin
Aug 16 12:34:13 localhost docker[2323]: time="2016-08-16T12:34:13.762838102Z" level=info msg="Graph migration to
Aug 16 12:34:13 localhost docker[2323]: time="2016-08-16T12:34:13.769883452Z" level=info msg="Firewalld running:
Aug 16 12:34:14 localhost docker[2323]: time="2016-08-16T12:34:14.023823826Z" level=info msg="Default bridge (do
Aug 16 12:34:14 localhost docker[2323]: time="2016-08-16T12:34:14.179897054Z" level=info msg="Loading containers
Aug 16 12:34:14 localhost docker[2323]: time="2016-08-16T12:34:14.179994020Z" level=info msg="Loading containers
Aug 16 12:34:14 localhost docker[2323]: time="2016-08-16T12:34:14.180008132Z" level=info msg="Daemon has complet
Aug 16 12:34:14 localhost docker[2323]: time="2016-08-16T12:34:14.180026066Z" level=info msg="Docker daemon" com
Aug 16 12:34:14 localhost docker[2323]: time="2016-08-16T12:34:14.187118716Z" level=info msg="API listen on 0.0.
Aug 16 12:34:14 localhost systemd[1]: Started Docker Application Container Engine.


ps aux | grep docker
root      2681  0.1  0.9 553580 35416 ?        Ssl  12:59   0:00 /usr/bin/docker daemon -H fd://
root      2694  0.0  0.3 287016 11724 ?        Ssl  12:59   0:00 docker-containerd -l /var/run/docker/libcontainerd/docker-containerd.sock --runtime docker-runc --start-timeout 2m
cuneyt    2835  0.0  0.0  11056  2228 pts/1    S+   13:01   0:00 grep docker

EDITAR : Cuando ejecuto manualmente, Docker Daemon funciona y la API escucha en /var/run/docker.sock

Cuando lo inicio con systemctl start docker API Escuche en 0.0.0.0:3000, creo que ese es el problema, pero no sé cómo solucionarlo, ¿alguna idea?

systemctl cat docker.service

[Service]
Type=notify
# the default is not to use systemd for cgroups because the delegate issues still
# exists and systemd currently does not support the cgroup feature set required
# for containers run by docker
ExecStart=/usr/bin/docker daemon -H fd://
MountFlags=slave
LimitNOFILE=1048576
LimitNPROC=1048576
LimitCORE=infinity
TimeoutStartSec=0
# set delegate yes so that systemd does not reset the cgroups of docker containers
Delegate=yes

[Install]
WantedBy=multi-user.target