Docker - Enable Remote HTTP API with SystemD and "daemon.json"
With a lot of fragmented documentation it was difficult to solve this.
My first solution was to create the daemon.json
with
{ "hosts": [ "unix:///var/run/docker.sock", "tcp://127.0.0.1:2376" ]}
This does not worked this error docker[5586]: unable to configure the Docker daemon with file /etc/docker/daemon.json
after tried to restart the daemon with service docker restart
.Note: There was more on the error that I failed to copy.
But what this error meant it at the start the daemon it a conflict with a flag and configurations on daemon.json
.
When I looked into it with service docker status
this it was the parent process: ExecStart=/usr/bin/docker daemon -H fd://
.
What it was strange because is different with configurations on /etc/init.d/docker
which I thought that were the service configurations.The strange part it was that the file on init.d
does contain any reference to daemon
argument neither -H fd://
.
After some research and a lot of searches of the system directories, I find out these directory (with help on the discussion on this issue docker github issue #22339).
Solution
Edited the ExecStart
from /lib/systemd/system/docker.service
with this new value:/usr/bin/docker daemon
And created the /etc/docker/daemon.json
with
{ "hosts": [ "fd://", "tcp://127.0.0.1:2376" ]}
Finally restarted the service with service docker start
and now I get the "green light" on service docker status
.
Tested the new configurations with:
$ docker run hello-worldHello from Docker!(...)
And,
$ curl http://127.0.0.1:2376/v1.23/info[JSON]
I hope that this will help someone with a similar problem as mine! :)
I had the same problem and actually in my eyes the easiest solution which should doesn't touch any existing files, which are managed by the system update process is, to use a systemd drop-in:Just create a file /etc/systemd/system/docker.service
which overwrites the specific part of the service in /lib/systemd/system/docker.service
.
In this case the content of /etc/systemd/system/docker.service
would be:
[Service]ExecStart=/usr/bin/dockerd --tlsverify --tlscacert=/etc/docker/ca.pem --tlscert=/etc/docker/server-cert.pem --tlskey=/etc/docker/server-key.pem -H=tcp://127.0.0.1:2375 -H=fd://
(You could even create a directory docker.service.d
which contains multiple files to overwrite different parameters.)
After adding the file you just run:
$ sudo systemctl daemon-reload$ sudo systemctl restart docker
The solution described at https://docs.docker.com/engine/admin/#troubleshoot-conflicts-between-the-daemonjson-and-startup-scripts works for me:
One notable example of a configuration conflict that is difficult to troubleshoot is when you want to specify a different daemon address from the default. Docker listens on a socket by default. On Debian and Ubuntu systems using
systemd
), this means that a-H
flag is always used when startingdockerd
. If you specify a hosts entry in thedaemon.json
, this causes a configuration conflict (as in the above message) and Docker fails to start.To work around this problem, create a new file
/etc/systemd/system/docker.service.d/docker.conf
with the following contents, to remove the-H
argument that is used when starting the daemon by default.
[Service]ExecStart=ExecStart=/usr/bin/dockerd
Note that the line with ExecStart=
is actually required, otherwise it'll fail with the error:
docker.service: Service has more than one ExecStart= setting, which is only allowed for Type=oneshot services. Refusing.
After creating the file you must run:
sudo systemctl daemon-reloadsudo systemctl restart docker