Article updated the 17th of August 2015, with the remarks of Giacomo Orlandi in the comments, who provided a cleaner way to update the systemd config, based on a discussion in this Docker’s Github issue.
If you upgraded (or fresh-installed) your box to Ubuntu 15.04, you may have noticed that the Docker daemon is not using the configuration defined in
/etc/default/docker anymore. That is due to the fact that Ubuntu is now using
systemd instead of Upstart/SysV. Unfortunately, Docker’s default systemd configuration is not ready for Ubuntu, and the config file is ignored.
First thing to do is to confirm that systemd is in charge of your Docker service. We can do that by simply asking systemd to give us Docker’s status, with the
systemctl status docker command :
$ systemctl status docker ● docker.service - Docker Application Container Engine Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled) Active: active (running) since mar. 2015-05-26 14:52:45 CEST; 58min ago Docs: http://docs.docker.com Main PID: 20075 (docker) Memory: 198.2M CGroup: /system.slice/docker.service ├─20075 /usr/bin/docker -d -H fd://
Two things are interresting in this output. The first one is that we can see that the docker daemon is launched with parameter
-H fd://, and nothing else (in my case, it should have some DNS declared, and an insecure registry - see the
DOCKER_OPTS line of your
/etc/default/docker file). The second one is that the systemd configuration file which is used is
Let’s see what it looks like :
$ cat /lib/systemd/system/docker.service [Unit] Description=Docker Application Container Engine Documentation=http://docs.docker.com After=network.target docker.socket Requires=docker.socket [Service] ExecStart=/usr/bin/docker -d -H fd:// MountFlags=slave LimitNOFILE=1048576 LimitNPROC=1048576 LimitCORE=infinity [Install] WantedBy=multi-user.target
Ahah ! Here is our issue: the execution command defined in the
ExecStart line is static: it does not use the variables defined in the
/etc/default/docker file. In order to have the file loaded, we need to declare
/etc/default/docker as an EnvironmentFile, and use the
DOCKER_OPTS variable in the
Systemd allow the user to override the default value in the config file by creating
*.conf files in a specific folder. We will need to create that folder, if it does not exist:
$ mkdir -p /etc/systemd/system/docker.service.d
Now, we can create our config override file in that folder :
$ vi /etc/systemd/system/docker.service.d/ubuntu.conf
containing the follwing lines:
[Service] # workaround to include default options EnvironmentFile=/etc/default/docker ExecStart= ExecStart=/usr/bin/docker -d -H fd:// $DOCKER_OPTS
Now, reload systemd’s config with
systemctl daemon-reload , and restart the Docker daemon in order to load the config file, with
systemctl restart docker, and run a
systemctl status docker to confirm that the config file has been loaded:
● docker.service - Docker Application Container Engine Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled) Drop-In: /etc/systemd/system/docker.service.d └─ubuntu.conf Active: active (running) since lun. 2015-08-17 15:29:39 CEST; 13min ago Docs: http://docs.docker.com Memory: 3.9M CGroup: /system.slice/docker.service ├─16089 /usr/bin/docker -d -H fd:// --dns 10.200.1.11 --dns 22.214.171.124 --insecure-registry insecure-registry:5000 └─17194 docker-proxy -proto tcp -host-ip 0.0.0.0 -host-port 43128 -container-ip 172.17.0.1 -container-port 3128
We can see the correct parameters in the Docker daemon command line, so it seems that
DOCKER_OPTS has been taken into account.
You will have one more thing to do if you declared variables other than
DOCKER_OPTS in the
/etc/default/docker file (ie. proxy configuration) : remove the exports. Systemd does not source the configuration file, it only loads declared variables into the process’ environment, so the lines that begin with
export will be ignored. If you have some of those lines in your configuration file, you will have to remove the word
export, and restart Docker’s daemon. The following
sed command will do that for you:
sed -i -e "s/^export //" -e "s/#export /#/" /etc/default/docker. Try to pull an image from Docker Hub in order to confirm that everything is OK.
With this workaround, you should be able to use Docker as usual on your Ubuntu 15.04 Vivid. However, don’t forget that it’s only a workaround, and not a very pretty one ! So be sure to update your Docker package as soon as Ubuntu Vivid’s compatibility is officialy fixed !
Thanks for reading, hope it helped.