https://docs.docker.com/config/daemon/

• Configure and troubleshoot（故障排解） the Docker daemon

After successfully installing and starting Docker, the dockerd daemon runs with its default configuration. This topic（主题） shows how to customize（自定义） the configuration, start the daemon manually（手动）, and troubleshoot（故障排解） and debug（调试） the daemon if you run into issues.

Start the daemon using operating system utilities（实用程序）

On a typical（典型的） installation the Docker daemon is started by a system utility, not manually by a user. This makes it easier to automatically start Docker when the machine reboots.

The command to start Docker depends on your operating system. Check the correct（正确的） page under Install Docker. To configure Docker to start automatically at system boot, see Configure Docker to start on boot.

Start the daemon manually

If you don’t want to use a system utility to manage the Docker daemon, or just want to test things out（测试问题）, you can manually run it using the dockerd command. You may need to use sudo, depending on your operating system configuration.

When you start Docker this way, it runs in the foreground（前台） and sends its logs directly（立即） to your terminal.

$ dockerd

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)

To stop Docker when you have started it manually, issue（发出...） a Ctrl+C in your terminal.

配置docker守护程序 Configure the Docker daemon

There are two ways to configure the Docker daemon:

• Use a JSON configuration file. This is the preferred（偏爱，推荐） option, since it keeps all configurations in a single place.
• Use flags when starting dockerd.

You can use both of these options together as long as you don’t specify（指定） the same option both as a flag and in the JSON file. If that happens, the Docker daemon won’t start and prints an error message.

只要不指定相同的选项作为标志和JSON文件，就可以同时使用这两个选项。 如果发生这种情况，Docker守护程序将不会启动并输出错误消息。

To configure the Docker daemon using a JSON file, create a file at /etc/docker/daemon.json on Linux systems, or C:\ProgramData\docker\config\daemon.json on Windows.

Here’s what the configuration file looks like:

{
  "debug": true,
  "tls": true,
  "tlscert": "/var/docker/server.pem",
  "tlskey": "/var/docker/serverkey.pem",
  "hosts": ["tcp://192.168.59.3:2376"]
}

With this configuration the Docker daemon runs in debug mode, uses TLS, and listens for traffic routed to 192.168.59.3 on port 2376. You can learn what configuration options are available in the dockerd reference docs

You can also start the Docker daemon manually and configure it using flags. This can be useful for troubleshooting problems.

Here’s an example of how to manually start the Docker daemon, using the same configurations as above:

dockerd --debug \
  --tls=true \
  --tlscert=/var/docker/server.pem \
  --tlskey=/var/docker/serverkey.pem \
  --host tcp://192.168.59.3:2376

You can learn what configuration options are available in the dockerd reference docs, or by running:

dockerd --help

Many specific（特性，细节） configuration options are discussed throughout（贯穿） the Docker documentation. Some places to go next include:

• Automatically start containers
• Limit a container’s resources
• Configure storage drivers
• Container security

Docker daemon directory

The Docker daemon persists（存留） all data in a single directory. This tracks everything related to Docker（它跟踪与Docker相关的所有内容）, including containers, images, volumes, service definition, and secrets.

By default this directory is:

• /var/lib/docker on Linux.
• C:\ProgramData\docker on Windows.

You can configure the Docker daemon to use a different directory, using the data-root configuration option.

Since the state of a Docker daemon is kept on this directory, make sure you use a dedicated directory for each daemon. If two daemons share the same directory, for example, an NFS share, you are going to experience errors that are difficult to troubleshoot.

由于Docker守护进程的状态保留在此目录中，因此请确保为每个守护进程使用专用目录。 如果两个守护程序共享相同的目录（例如NFS共享），则您将遇到难以排除故障的错误。

Troubleshoot the daemon

You can enable debugging on the daemon to learn about the runtime activity of the daemon and to aid（有助于） in troubleshooting. If the daemon is completely non-responsive（无响应）, you can also force a full stack trace of all threads to be added to the daemon log by sending the SIGUSR signal to the Docker daemon.

Troubleshoot conflicts between the daemon.json and startup scripts

If you use a daemon.json file and also pass options to the dockerd command manually or using start-up scripts, and these options conflict, Docker fails to start with an error such as:

unable to configure the Docker daemon with file /etc/docker/daemon.json:
the following directives are specified both as a flag and in the configuration
file: hosts: (from flag: [unix:///var/run/docker.sock], from file: [tcp://127.0.0.1:2376])

If you see an error similar to this one and you are starting the daemon manually with flags, you may need to adjust（调整） your flags or the daemon.json to remove the conflict.

Note: If you see this specific error, continue to the next section for a workaround.

If you are starting Docker using your operating system’s init scripts, you may need to override the defaults in these scripts in ways that are specific to the operating system.

USE THE HOSTS KEY IN DAEMON.JSON WITH SYSTEMD

One notable（值得注意的） 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 host flag -H is always used when starting dockerd. If you specify a hosts entry in the daemon.json, this causes a configuration conflict (as in the above message) and Docker fails to start.

To work around this problem（解决这个问题）, create a new file /etc/systemd/system/docker.service.d/docker.confwith the following contents, to remove the -H argument that is used when starting the daemon by default.

[Service]
ExecStart=
ExecStart=/usr/bin/dockerd

There are other times when you might need to configure systemd with Docker, such as configuring a HTTP or HTTPS proxy.

Note: If you override this option and then do not specify a hosts entry in the daemon.json or a -H flag when starting Docker manually, Docker fails to start.

Run sudo systemctl daemon-reload before attempting to start Docker. If Docker starts successfully, it is now listening on the IP address specified in the hosts key of the daemon.json instead of a socket.

Important: Setting hosts in the daemon.json is not supported on Docker for Windows or Docker for Mac.

Out Of Memory Exceptions (OOME)

If your containers attempt to use more memory than the system has available, you may experience an Out Of Memory Exception (OOME) and a container, or the Docker daemon, might be killed by the kernel OOM killer. To prevent（预防，阻止） this from happening, ensure that your application runs on hosts with adequate（充足的） memory and see Understand the risks of running out of memory.

Read the logs

The daemon logs may help you diagnose（诊断） problems. The logs may be saved in one of a few locations, depending on the operating system configuration and the logging subsystem used:

Operating system	Location
RHEL, Oracle Linux	/var/log/messages
Debian	/var/log/daemon.log
Ubuntu 16.04+, CentOS	Use the command journalctl -u docker.service
Ubuntu 14.10-	/var/log/upstart/docker.log
macOS (Docker 18.01+)	~/Library/Containers/com.docker.docker/Data/vms/0/console-ring
macOS (Docker <18.01)	~/Library/Containers/com.docker.docker/Data/com.docker.driver.amd64-linux/console-ring
Windows	AppData\Local

Enable debugging

There are two ways to enable debugging. The recommended approach（方法） is to set the debug key to true in the daemon.json file. This method works for every Docker platform.

1. Edit the daemon.json file, which is usually located in /etc/docker/. You may need to create this file, if it does not yet exist. On macOS or Windows, do not edit the file directly. Instead, go toPreferences / Daemon / Advanced.

2. If the file is empty, add the following:

   {
     "debug": true
   }
   
   

   If the file already contains JSON, just add the key "debug": true, being careful to add a comma to the end of the line if it is not the last line before the closing bracket. Also verify that if the log-level key is set, it is set to either info or debug. info is the default, and possible values are debug, info, warn, error, fatal.

3. Send a HUP signal to the daemon to cause it to reload its configuration. On Linux hosts, use the following command.

   $ sudo kill -SIGHUP $(pidof dockerd)
   

   On Windows hosts, restart Docker.

Instead of following this procedure, you can also stop the Docker daemon and restart it manually with the debug flag -D. However, this may result in Docker restarting with a different environment than the one the hosts’ startup scripts create, and this may make debugging more difficult.

强制堆栈跟踪被记录 Force a stack trace to be logged

If the daemon is unresponsive, you can force a full stack trace to be logged by sending a SIGUSR1signal to the daemon.

• Linux:

  $ sudo kill -SIGUSR1 $(pidof dockerd)
  
  

• Windows Server:

  Download docker-signal.

  Run the executable with the flag --pid=<PID of daemon>.

This forces a stack trace to be logged but does not stop the daemon. Daemon logs show the stack trace or the path to a file containing the stack trace if it was logged to a file.

The daemon continues operating after handling the SIGUSR1 signal and dumping（倾泻） the stack traces to the log. The stack traces can be used to determine the state of all goroutines and threads within the daemon.（堆栈跟踪可用于确定守护进程内所有goroutine和线程的状态。）

查看堆栈 View stack traces

The Docker daemon log can be viewed by using one of the following methods:

• By running journalctl -u docker.service on Linux systems using systemctl
• /var/log/messages, /var/log/daemon.log, or /var/log/docker.log on older Linux systems
• By running Get-EventLog -LogName Application -Source Docker -After (Get-Date).AddMinutes(-5) | Sort-Object Time | Export-CSV ~/last5minutes.CSVon Docker EE for Windows Server

Note: It is not possible to manually generate a stack trace on Docker for Mac or Docker for Windows. However, you can click the Docker taskbar icon and choose Diagnose and feedback to send information to Docker if you run into issues.

Look in the Docker logs for a message like the following:

...goroutine stacks written to /var/run/docker/goroutine-stacks-2017-06-02T193336z.log
...daemon datastructure dump written to /var/run/docker/daemon-data-2017-06-02T193336z.log

The locations where Docker saves these stack traces and dumps depends on your operating system and configuration. You can sometimes get useful diagnostic information straight（直接的） from the stack traces and dumps. Otherwise, you can provide this information to Docker for help diagnosing the problem.

检查docker 是否运行 Check whether Docker is running

The operating-system independent way to check whether Docker is running is to ask Docker, using the docker info command.

You can also use operating system utilities, such as sudo systemctl is-active docker or sudo status docker or sudo service docker status, or checking the service status using Windows utilities.

Finally, you can check in the process list for the dockerd process, using commands like ps or top.