DOCKER_HOST needs to be setup to access docker daemon from non-root in devstack setup

[janonymous]

=========================
DevStack Component Timing
=========================
Total runtime 439

run_process 64
test_with_retry 1
apt-get-update 14
pip_install 66
restart_apache_server 9
wait_for_service 8
apt-get 5
=========================

This is your host IP address: 10.0.2.15
This is your host IPv6 address: ::1
Horizon is now available at http://10.0.2.15/dashboard
Keystone is serving at http://10.0.2.15/identity/
The default users are: admin and demo
The password: pass
vagrant@devstack:~/devstack$ ps -efa | grep docker
vagrant 2482 24308 0 05:07 pts/26 00:00:00 grep docker
root 25893 25868 0 05:00 pts/6 00:00:00 sudo /usr/bin/docker daemon -H tcp://0.0.0.0:2375 --cluster-store etcd://localhost:4001
root 25896 25893 0 05:00 pts/6 00:00:00 dockerd -H tcp://0.0.0.0:2375 --cluster-store etcd://localhost:4001
root 25939 25896 0 05:00 ? 00:00:00 docker-containerd -l unix:///var/run/docker/libcontainerd/docker-containerd.sock --shim docker-containerd-shim --metrics-interval=0 --start-timeout 2m --state-dir /var/run/docker/libcontainerd/containerd --runtime docker-runc
vagrant@devstack:~/devstack$ sudo docker ps
Cannot connect to the Docker daemon. Is the docker daemon running on this host?
vagrant@devstack:~/devstack$ docker ps
Error response from daemon: {
  "Err": "404: Not Found"
}
vagrant@devstack:~/devstack$

After Setting DOCKER_HOST env variable

vagrant@devstack:~/devstack$ export DOCKER_HOST=tcp://0.0.0.0:2375
vagrant@devstack:~/devstack$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

Additional Info 2375 is available for tcp6... :

vagrant@devstack:~/devstack$ sudo netstat -anlpto | grep "docker"
tcp 0 0 127.0.0.1:35751 127.0.0.1:4001 ESTABLISHED 25896/dockerd keepalive (17.29/0/0)
tcp 0 0 127.0.0.1:35750 127.0.0.1:4001 ESTABLISHED 25896/dockerd keepalive (19.59/0/0)
tcp6 0 0 :::2375 :::* LISTEN 25896/dockerd off (0.00/0/0)
vagrant@devstack:~/devstack$ sudo netstat -anlpto | grep "kuryr"
vagrant@devstack:~/devstack$ sudo ps -eaf | grep "kuryr"
root 1790 1760 0 05:02 pts/24 00:00:00 sudo PYTHONPATH=:/opt/stack/kuryr SERVICE_USER=admin SERVICE_PASSWORD=pass SERVICE_TENANT_NAME=admin SERVICE_TOKEN=pass IDENTITY_URL=http://127.0.0.1:5000/v2.0 python /opt/stack/kuryr-libnetwork/scripts/run_server.py --config-file /etc/kuryr/kuryr.conf
root 1792 1790 0 05:02 pts/24 00:00:00 python /opt/stack/kuryr-libnetwork/scripts/run_server.py --config-file /etc/kuryr/kuryr.conf
vagrant 4050 24308 0 05:17 pts/26 00:00:00 grep kuryr
vagrant@devstack:~/devstack$ sudo netstat -anlp | grep 23750
tcp 0 0 127.0.0.1:23750 0.0.0.0:* LISTEN 1792/python

[janonymous (janonymous)]

One more observation that

***When docker is run through tcp://0.0.0.0:2375 ***
--------------------------------------------------------------------------------------------------
vagrant@devstack:~/devstack$ sudo netstat -anlpto | grep "docker"
tcp 0 0 127.0.0.1:36101 127.0.0.1:4001 ESTABLISHED 7268/dockerd keepalive (12.90/0/0)
tcp 0 0 127.0.0.1:36100 127.0.0.1:4001 ESTABLISHED 7268/dockerd keepalive (12.90/0/0)
tcp6 0 0 :::2375 :::* LISTEN 7268/dockerd off (0.00/0/0)
--------------------------------------------------------------------------------------------------

vagrant@devstack:~/devstack$ sudo /usr/bin/docker daemon -H tcp://0.0.0.0:2375 --cluster-store etcd://localhost:4001 & echo $! >/opt/stack/status/stack/docker-engine.pid; fg || echo "docker-engine failed to start" | tee "/opt/stack/status/stack/docker-engine.failure"
[1] 7267
sudo /usr/bin/docker daemon -H tcp://0.0.0.0:2375 --cluster-store etcd://localhost:4001
WARN[0000] [!] DON'T BIND ON ANY IP ADDRESS WITHOUT setting -tlsverify IF YOU DON'T KNOW WHAT YOU'RE DOING [!]
INFO[0000] libcontainerd: new containerd process, pid: 7276
WARN[0000] containerd: low RLIMIT_NOFILE changing to max current=1024 max=4096
INFO[0001] [graphdriver] using prior storage driver "aufs"
INFO[0001] Graph migration to content-addressability took 0.00 seconds
WARN[0001] Your kernel does not support swap memory limit.
WARN[0001] mountpoint for pids not found
INFO[0001] Loading containers: start.
INFO[0001] Firewalld running: false
INFO[0001] Default bridge (docker0) is assigned with an IP address 172.17.0.0/16. Daemon option --bip can be used to set a preferred IP address

INFO[0001] Loading containers: done.
INFO[0001] Daemon has completed initialization
INFO[0001] Docker daemon commit=23cf638 graphdriver=aufs version=1.12.1
INFO[0001] API listen on [::]:2375

***When docker is run through tcp://127.0.0.1:2375 ***
----------------------------------------------------------------------------------------------------
vagrant@devstack:~/devstack$ sudo netstat -anlpto | grep "docker"
tcp 0 0 127.0.0.1:2375 0.0.0.0:* LISTEN 5435/dockerd off (0.00/0/0)
tcp 0 0 127.0.0.1:36083 127.0.0.1:4001 ESTABLISHED 5435/dockerd keepalive (13.90/0/0)
tcp 0 0 127.0.0.1:36084 127.0.0.1:4001 ESTABLISHED 5435/dockerd keepalive (13.13/0/0)
----------------------------------------------------------------------------------------------------

vagrant@devstack:~/devstack$ sudo /usr/bin/docker daemon -H tcp://127.0.0.1:2375 --cluster-store etcd://localhost:4001 & echo $! >/opt/stack/status/stack/docker-engine.pid; fg || echo "docker-engine failed to start" | tee "/opt/stack/status/stack/docker-engine.failure"
[1] 5434
sudo /usr/bin/docker daemon -H tcp://127.0.0.1:2375 --cluster-store etcd://localhost:4001
WARN[0000] [!] DON'T BIND ON ANY IP ADDRESS WITHOUT se...

[janonymous (janonymous)]

Granting permissions to access the socket files solves the issue to explicitly set docker_host
https://review.openstack.org/#/c/370598/