moby--moby/docs/articles/configuring.md

Configuring and running Docker on various distributions

After successfully installing Docker, the docker daemon runs with its default configuration.

In a production environment, system administrators typically configure the docker daemon to start and stop according to an organization's requirements. In most cases, the system administrator configures a process manager such as SysVinit, Upstart, or systemd to manage the docker daemon's start and stop.

Running the docker daemon directly

The docker daemon can be run directly using the -d option. By default it listens on the Unix socket unix:///var/run/docker.sock

$ docker -d

INFO[0000] +job init_networkdriver()
INFO[0000] +job serveapi(unix:///var/run/docker.sock)
INFO[0000] Listening for HTTP on unix (/var/run/docker.sock)
...
...

Configuring the docker daemon directly

If you're running the docker daemon directly by running docker -d instead of using a process manager, you can append the configuration options to the docker run command directly. Just like the -d option, other options can be passed to the docker daemon to configure it.

Some of the daemon's options are:

Flag	Description
-D, --debug=false	Enable or disable debug mode. By default, this is false.
-H,--host=[]	Daemon socket(s) to connect to.
--tls=false	Enable or disable TLS. By default, this is false.

Here is a an example of running the docker daemon with configuration options:

$ docker -d -D --tls=true --tlscert=/var/docker/server.pem --tlskey=/var/docker/serverkey.pem -H tcp://192.168.59.3:2376

These options :

• Enable -D (debug) mode
• Set tls to true with the server certificate and key specified using --tlscert and --tlskey respectively
• Listen for connections on tcp://192.168.59.3:2376

The command line reference has the complete list of daemon flags with explanations.

Ubuntu

As of 14.04, Ubuntu uses Upstart as a process manager. By default, Upstart jobs are located in /etc/init and the docker Upstart job can be found at /etc/init/docker.conf.

After successfully installing Docker for Ubuntu, you can check the running status using Upstart in this way:

$ sudo status docker

docker start/running, process 989

Running Docker

You can start/stop/restart the docker daemon using

$ sudo start docker

$ sudo stop docker

$ sudo restart docker

Configuring Docker

You configure the docker daemon in the /etc/default/docker file on your system. You do this by specifying values in a DOCKER_OPTS variable.

To configure Docker options:

1. Log into your host as a user with sudo or root privileges.

2. If you don't have one, create the /etc/default/docker file on your host. Depending on how you installed Docker, you may already have this file.

3. Open the file with your favorite editor.

   $ sudo vi /etc/default/docker
   

4. Add a DOCKER_OPTS variable with the following options. These options are appended to the docker daemon's run command.

    DOCKER_OPTS="-D --tls=true --tlscert=/var/docker/server.pem --tlskey=/var/docker/serverkey.pem -H tcp://192.168.59.3:2376"

These options :

• Enable -D (debug) mode
• Set tls to true with the server certificate and key specified using --tlscert and --tlskey respectively
• Listen for connections on tcp://192.168.59.3:2376

The command line reference has the complete list of daemon flags with explanations.

5. Save and close the file.

6. Restart the docker daemon.

   $ sudo restart docker
   

7. Verify that the docker daemon is running as specified with the ps command.

   $ ps aux | grep docker | grep -v grep
   

Logs

By default logs for Upstart jobs are located in /var/log/upstart and the logs for docker daemon can be located at /var/log/upstart/docker.log

$ tail -f /var/log/upstart/docker.log
INFO[0000] Loading containers: done.
INFO[0000] docker daemon: 1.6.0 4749651; execdriver: native-0.2; graphdriver: aufs
INFO[0000] +job acceptconnections()
INFO[0000] -job acceptconnections() = OK (0)
INFO[0000] Daemon has completed initialization

CentOS / Red Hat Enterprise Linux / Fedora

As of 7.x, CentOS and RHEL use systemd as the process manager. As of 21, Fedora uses systemd as its process manager.

After successfully installing Docker for CentOS/[Red Hat Enterprise Linux] (/installation/rhel/)/Fedora, you can check the running status in this way:

$ sudo systemctl status docker

Running Docker

You can start/stop/restart the docker daemon using

$ sudo systemctl start docker

$ sudo systemctl stop docker

$ sudo systemctl restart docker

If you want Docker to start at boot, you should also:

$ sudo systemctl enable docker

Configuring Docker

You configure the docker daemon in the /etc/sysconfig/docker file on your host. You do this by specifying values in a variable. For CentOS 7.x and RHEL 7.x, the name of the variable is OPTIONS and for CentOS 6.x and RHEL 6.x, the name of the variable is other_args. For this section, we will use CentOS 7.x as an example to configure the docker daemon.

By default, systemd services are located either in /etc/systemd/service, /lib/systemd/system or /usr/lib/systemd/system. The docker.service file can be found in either of these three directories depending on your host.

To configure Docker options:

1. Log into your host as a user with sudo or root privileges.

2. If you don't have one, create the /etc/sysconfig/docker file on your host. Depending on how you installed Docker, you may already have this file.

3. Open the file with your favorite editor.

   $ sudo vi /etc/sysconfig/docker
   

4. Add a OPTIONS variable with the following options. These options are appended to the command that starts the docker daemon.

    OPTIONS="-D --tls=true --tlscert=/var/docker/server.pem --tlskey=/var/docker/serverkey.pem -H tcp://192.168.59.3:2376"

These options :

• Enable -D (debug) mode
• Set tls to true with the server certificate and key specified using --tlscert and --tlskey respectively
• Listen for connections on tcp://192.168.59.3:2376

The command line reference has the complete list of daemon flags with explanations.

5. Save and close the file.

6. Restart the docker daemon.

   $ sudo service docker restart
   

7. Verify that the docker daemon is running as specified with the ps command.

   $ ps aux | grep docker | grep -v grep
   

Logs

systemd has its own logging system called the journal. The logs for the docker daemon can be viewed using journalctl -u docker

$ sudo journalctl -u docker
May 06 00:22:05 localhost.localdomain systemd[1]: Starting Docker Application Container Engine...
May 06 00:22:05 localhost.localdomain docker[2495]: time="2015-05-06T00:22:05Z" level="info" msg="+job serveapi(unix:///var/run/docker.sock)"
May 06 00:22:05 localhost.localdomain docker[2495]: time="2015-05-06T00:22:05Z" level="info" msg="Listening for HTTP on unix (/var/run/docker.sock)"
May 06 00:22:06 localhost.localdomain docker[2495]: time="2015-05-06T00:22:06Z" level="info" msg="+job init_networkdriver()"
May 06 00:22:06 localhost.localdomain docker[2495]: time="2015-05-06T00:22:06Z" level="info" msg="-job init_networkdriver() = OK (0)"
May 06 00:22:06 localhost.localdomain docker[2495]: time="2015-05-06T00:22:06Z" level="info" msg="Loading containers: start."
May 06 00:22:06 localhost.localdomain docker[2495]: time="2015-05-06T00:22:06Z" level="info" msg="Loading containers: done."
May 06 00:22:06 localhost.localdomain docker[2495]: time="2015-05-06T00:22:06Z" level="info" msg="docker daemon: 1.5.0-dev fc0329b/1.5.0; execdriver: native-0.2; graphdriver: devicemapper"
May 06 00:22:06 localhost.localdomain docker[2495]: time="2015-05-06T00:22:06Z" level="info" msg="+job acceptconnections()"
May 06 00:22:06 localhost.localdomain docker[2495]: time="2015-05-06T00:22:06Z" level="info" msg="-job acceptconnections() = OK (0)"

Note: Using and configuring journal is an advanced topic and is beyond the scope of this article.