github.com/circular-dark/docker@v1.7.0/docs/articles/configuring.md

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title = "Configuring and running Docker"
description = "Configuring and running the Docker daemon on various distributions"
keywords = ["docker, daemon, configuration, running,  process managers"]
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parent = "smn_administrate"
weight = 3
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# 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](/reference/commandline/cli/#daemon)
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](/installation/ubuntulinux/),
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](/reference/commandline/cli/#daemon)
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](/installation/centos/)/[Red Hat Enterprise Linux]
(/installation/rhel/)/[Fedora](/installation/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](/reference/commandline/cli/#daemon)
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._