1. Debian Start Docker Service
  2. Debian Run Docker
  3. Debian Start Docker Daemon
  4. Linux Start Docker
  5. Debian Start Docker Daemon
  6. Debian Start Docker Container On Boot

Estimated reading time: 11 minutes

Docker service will not start on Debian on wsl2 #4872. Step 2 – Install Docker CE on Debian 10. We need to install Docker engine on all the hosts, manager and worker nodes. Install dependency packages on the hosts: sudo apt-get update sudo apt-get install apt-transport-https ca-certificates curl gnupg-agent software-properties-common Add Docker GPG key.

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Debian images are available in the docker.io official repository, but you may as well create some yourself (see more details on both options below). In Docker terminology, an image is an object that you can download, and reuse to instantiate new containers. Ready-made images from docker.io's official Debian repository. Sudo apt-get update sudo apt-get install docker-ce docker-ce-cli containerd.io If you find something wrong along the line, maybe you are missing some features needed for the complete installation. Since the documentation includes steps you probably don't need if you have gone through some dev setup before, I cut it outhere.

After successfully installing and starting Docker, the dockerd daemonruns with its default configuration. This topic shows how to customizethe configuration, start the daemon manually, and troubleshoot and debug thedaemon if you run into issues.

Start the daemon using operating system utilities

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

The command to start Docker depends on your operating system. Check the correctpage under Install Docker. To configure Dockerto start automatically at system boot, seeConfigure Docker to start on boot.

Start the daemon manually

If you don’t want to use a system utility to manage the Docker daemon, orjust want to test things out, you can manually run it using the dockerdcommand. You may need to use sudo, depending on your operating systemconfiguration.

When you start Docker this way, it runs in the foreground and sends its logsdirectly to your terminal.

To stop Docker when you have started it manually, issue a Ctrl+C in yourterminal.

Configure the Docker daemon

There are two ways to configure the Docker daemon:

  • Use a JSON configuration file. This is the preferred option, since it keepsall 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 thesame option both as a flag and in the JSON file. If that happens, the Dockerdaemon won’t start and prints an error message.

To configure the Docker daemon using a JSON file, create a file at/etc/docker/daemon.json on Linux systems, or C:ProgramDatadockerconfigdaemon.jsonon Windows. On MacOS go to the whale in the taskbar > Preferences > Daemon > Advanced.

Here’s what the configuration file looks like:

Debian Start Docker

With this configuration the Docker daemon runs in debug mode, uses TLS, andlistens for traffic routed to 192.168.59.3 on port 2376.You can learn what configuration options are available in thedockerd 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 sameconfigurations as above:

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

Many specific configuration options are discussed throughout the Dockerdocumentation. Some places to go next include:

Docker daemon directory

The Docker daemon persists all data in a single directory. This tracks everythingrelated to Docker, including containers, images, volumes, service definition,and secrets.

By default this directory is:

  • /var/lib/docker on Linux.
  • C:ProgramDatadocker on Windows.

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

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

Troubleshoot the daemon

You can enable debugging on the daemon to learn about the runtime activity ofthe daemon and to aid in troubleshooting. If the daemon is completelynon-responsive, you can alsoforce a full stack trace of allthreads to be added to the daemon log by sending the SIGUSR signal to theDocker daemon.

Troubleshoot conflicts between the daemon.json and startup scripts

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

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

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

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

Use the hosts key in daemon.json with systemd

Debian run docker as non root

One notable example of a configuration conflict that is difficult to troubleshootis when you want to specify a different daemon address fromthe 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 ahosts 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, create a new file /etc/systemd/system/docker.service.d/docker.conf withthe following contents, to remove the -H argument that is used when starting the daemon by default.

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

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

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

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

Debian Start Docker Service

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 theDocker daemon, might be killed by the kernel OOM killer. To prevent this fromhappening, ensure that your application runs on hosts with adequate memory andseeUnderstand the risks of running out of memory.

Read the logs

The daemon logs may help you diagnose problems. The logs may be saved in one ofa few locations, depending on the operating system configuration and the loggingsubsystem used:

Operating systemLocation
RHEL, Oracle Linux/var/log/messages
Debian/var/log/daemon.log
Ubuntu 16.04+, CentOSUse the command journalctl -u docker.service or /var/log/syslog
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
WindowsAppDataLocal

Enable debugging

There are two ways to enable debugging. The recommended approach is to set thedebug key to true in the daemon.json file. This method works for everyDocker 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 orWindows, do not edit the file directly. Instead, go toPreferences / Daemon / Advanced.

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

    If the file already contains JSON, just add the key 'debug': true, beingcareful to add a comma to the end of the line if it is not the last linebefore 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 possiblevalues 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.

    On Windows hosts, restart Docker.

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

Force a stack trace to be logged

If the daemon is unresponsive, you can force a full stack trace to be loggedby sending a SIGUSR1 signal to the daemon.

  • Linux:

  • Windows Server:

    Download docker-signal.

    Get the process ID of dockerd Get-Process dockerd.

    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 thestack trace if it was logged to a file.

The daemon continues operating after handling the SIGUSR1 signal anddumping the stack traces to the log. The stack traces can be used to determinethe state of all goroutines and threads within the daemon.

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 olderLinux systems

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

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

The locations where Docker saves these stack traces and dumps depends on youroperating system and configuration. You can sometimes get useful diagnosticinformation straight from the stack traces and dumps. Otherwise, you can providethis information to Docker for help diagnosing the problem.

Check whether Docker is running

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

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

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

docker, daemon, configuration, troubleshooting

Estimated reading time: 15 minutes

This section contains optional procedures for configuring Linux hosts to workbetter with Docker.

Manage Docker as a non-root user

The Docker daemon binds to a Unix socket instead of a TCP port. By defaultthat Unix socket is owned by the user root and other users can only access itusing sudo. The Docker daemon always runs as the root user.

If you don’t want to preface the docker command with sudo, create a Unixgroup called docker and add users to it. When the Docker daemon starts, itcreates a Unix socket accessible by members of the docker group.

Warning

Debian Run Docker

The docker group grants privileges equivalent to the rootuser. For details on how this impacts security in your system, seeDocker Daemon Attack Surface.

Note:

To run Docker without root privileges, seeRun the Docker daemon as a non-root user (Rootless mode).

To create the docker group and add your user:

  1. Create the docker group.

  2. Add your user to the docker group.

  3. Log out and log back in so that your group membership is re-evaluated.

    If testing on a virtual machine, it may be necessary to restart the virtual machine for changes to take effect.

    On a desktop Linux environment such as X Windows, log out of your session completely and then log back in.

    On Linux, you can also run the following command to activate the changes to groups:

  4. Verify that you can run docker commands without sudo.

    This command downloads a test image and runs it in a container. When thecontainer runs, it prints an informational message and exits.

    If you initially ran Docker CLI commands using sudo before addingyour user to the docker group, you may see the following error,which indicates that your ~/.docker/ directory was created withincorrect permissions due to the sudo commands.

    To fix this problem, either remove the ~/.docker/ directory(it is recreated automatically, but any custom settingsare lost), or change its ownership and permissions using thefollowing commands:

Configure Docker to start on boot

Most current Linux distributions (RHEL, CentOS, Fedora, Debian, Ubuntu 16.04 andhigher) use systemd to manage which services start when the systemboots. On Debian and Ubuntu, the Docker service is configured to start on bootby default. To automatically start Docker and Containerd on boot for otherdistros, use the commands below:

To disable this behavior, use disable instead.

If you need to add an HTTP Proxy, set a different directory or partition for theDocker runtime files, or make other customizations, seecustomize your systemd Docker daemon options.

Use a different storage engine

For information about the different storage engines, seeStorage drivers.The default storage engine and the list of supported storage engines depend onyour host’s Linux distribution and available kernel drivers.

Configure default logging driver

Docker provides the capability tocollect and view log data from all containers running on a host via a series oflogging drivers. The default logging driver, json-file, writes log data toJSON-formatted files on the host filesystem. Over time, these log files expandin size, leading to potential exhaustion of disk resources.

To alleviate such issues, either configure the json-file logging driver toenable log rotation, use analternative logging driversuch as the “local” logging driverthat performs log rotation by default, or use a logging driver that sendslogs to a remote logging aggregator.

Configure where the Docker daemon listens for connections

By default, the Docker daemon listens for connections on a UNIX socket to acceptrequests from local clients. It is possible to allow Docker to accept requestsfrom remote hosts by configuring it to listen on an IP address and port as wellas the UNIX socket. For more detailed information on this configuration optiontake a look at “Bind Docker to another host/port or a unix socket” section ofthe Docker CLI Reference article.

Secure your connection

Before configuring Docker to accept connections from remote hosts it is critically important that youunderstand the security implications of opening docker to the network. If steps are not taken to secure the connection, it is possible for remote non-root users to gain root access on the host. For more information on how to use TLS certificates to secure this connection, check this article on how to protect the Docker daemon socket.

Configuring Docker to accept remote connections can be done with the docker.servicesystemd unit file for Linux distributions using systemd, such as recent versionsof RedHat, CentOS, Ubuntu and SLES, or with the daemon.json file which isrecommended for Linux distributions that do not use systemd.

systemd vs daemon.json

Configuring Docker to listen for connections using both the systemd unit file and the daemon.json file causes a conflict that prevents Docker from starting.

Configuring remote access with systemd unit file

  1. Use the command sudo systemctl edit docker.service to open an override file for docker.service in a text editor.

  2. Add or modify the following lines, substituting your own values.

  3. Save the file.

  4. Reload the systemctl configuration.

  5. Restart Docker.

  6. Check to see whether the change was honored by reviewing the output of netstat to confirm dockerd is listening on the configured port.

Configuring remote access with daemon.json

  1. Set the hosts array in the /etc/docker/daemon.json to connect to the UNIX socket and an IP address, as follows:

  2. Restart Docker.

  3. Check to see whether the change was honored by reviewing the output of netstat to confirm dockerd is listening on the configured port.

Enable IPv6 on the Docker daemon

To enable IPv6 on the Docker daemon, seeEnable IPv6 support.

Troubleshooting

Kernel compatibility

Debian Start Docker Daemon

Docker cannot run correctly if your kernel is older than version 3.10 or if itis missing some modules. To check kernel compatibility, you can download andrun the check-config.shscript.

The script only works on Linux, not macOS.

Cannot connect to the Docker daemon

If you see an error such as the following, your Docker client may be configuredto connect to a Docker daemon on a different host, and that host may not bereachable.

To see which host your client is configured to connect to, check the value ofthe DOCKER_HOST variable in your environment.

If this command returns a value, the Docker client is set to connect to aDocker daemon running on that host. If it is unset, the Docker client is set toconnect to the Docker daemon running on the local host. If it is set in error,use the following command to unset it:

You may need to edit your environment in files such as ~/.bashrc or~/.profile to prevent the DOCKER_HOST variable from being seterroneously.

If DOCKER_HOST is set as intended, verify that the Docker daemon is runningon the remote host and that a firewall or network outage is not preventing youfrom connecting.

IP forwarding problems

If you manually configure your network using systemd-network with systemdversion 219 or higher, Docker containers may not be able to access your network.Beginning with systemd version 220, the forwarding setting for a given network(net.ipv4.conf.<interface>.forwarding) defaults to off. This settingprevents IP forwarding. It also conflicts with Docker’s behavior of enablingthe net.ipv4.conf.all.forwarding setting within containers.

To work around this on RHEL, CentOS, or Fedora, edit the <interface>.networkfile in /usr/lib/systemd/network/ on your Docker host(ex: /usr/lib/systemd/network/80-container-host0.network) and add thefollowing block within the [Network] section.

This configuration allows IP forwarding from the container as expected.

DNS resolver found in resolv.conf and containers can't use it

Linux systems which use a GUI often have a network manager running, which uses adnsmasq instance running on a loopback address such as 127.0.0.1 or127.0.1.1 to cache DNS requests, and adds this entry to/etc/resolv.conf. The dnsmasq service speeds upDNS look-ups and also provides DHCP services. This configuration does not workwithin a Docker container which has its own network namespace, becausethe Docker container resolves loopback addresses such as 127.0.0.1 toitself, and it is very unlikely to be running a DNS server on its ownloopback address.

If Docker detects that no DNS server referenced in /etc/resolv.conf is a fullyfunctional DNS server, the following warning occurs and Docker uses the publicDNS servers provided by Google at 8.8.8.8 and 8.8.4.4 for DNS resolution.

If you see this warning, first check to see if you use dnsmasq:

If your container needs to resolve hosts which are internal to your network, thepublic nameservers are not adequate. You have two choices:

  • You can specify a DNS server for Docker to use, or
  • You can disable dnsmasq in NetworkManager. If you do this, NetworkManageradds your true DNS nameserver to /etc/resolv.conf, but you lose thepossible benefits of dnsmasq.

You only need to use one of these methods.

Specify DNS servers for Docker

The default location of the configuration file is /etc/docker/daemon.json. Youcan change the location of the configuration file using the --config-filedaemon flag. The documentation below assumes the configuration file is locatedat /etc/docker/daemon.json.

  1. Create or edit the Docker daemon configuration file, which defaults to/etc/docker/daemon.json file, which controls the Docker daemonconfiguration.

  2. Add a dns key with one or more IP addresses as values. If the file hasexisting contents, you only need to add or edit the dns line.

    If your internal DNS server cannot resolve public IP addresses, include atleast one DNS server which can, so that you can connect to Docker Hub and sothat your containers can resolve internet domain names.

    Save and close the file.

  3. Restart the Docker daemon.

  4. Verify that Docker can resolve external IP addresses by trying to pull animage:

  5. If necessary, verify that Docker containers can resolve an internal hostnameby pinging it.

Disable dnsmasq

Ubuntu

If you prefer not to change the Docker daemon’s configuration to use a specificIP address, follow these instructions to disable dnsmasq in NetworkManager.

  1. Edit the /etc/NetworkManager/NetworkManager.conf file.

  2. Comment out the dns=dnsmasq line by adding a # character to the beginningof the line.

    Save and close the file.

  3. Restart both NetworkManager and Docker. As an alternative, you can rebootyour system.

RHEL, CentOS, or Fedora

Linux Start Docker

To disable dnsmasq on RHEL, CentOS, or Fedora:

  1. Disable the dnsmasq service:

  2. Configure the DNS servers manually using theRed Hat documentation.

Allow access to the remote API through a firewall

If you run a firewall on the same host as you run Docker and you want to accessthe Docker Remote API from another host and remote access is enabled, you needto configure your firewall to allow incoming connections on the Docker port,which defaults to 2376 if TLS encrypted transport is enabled or 2375otherwise.

Docker

Two common firewall daemons areUFW (Uncomplicated Firewall) (oftenused for Ubuntu systems) and firewalld (often usedfor RPM-based systems). Consult the documentation for your OS and firewall, butthe following information might help you get started. These options are fairlypermissive and you may want to use a different configuration that locks yoursystem down more.

  • UFW: Set DEFAULT_FORWARD_POLICY='ACCEPT' in your configuration.

  • firewalld: Add rules similar to the following to your policy (one forincoming requests and one for outgoing requests). Be sure the interface namesand chain names are correct.

Your kernel does not support cgroup swap limit capabilities

On Ubuntu or Debian hosts, You may see messages similar to the following whenworking with an image.

Docker

This warning does not occur on RPM-based systems, which enable thesecapabilities by default.

If you don’t need these capabilities, you can ignore the warning. You can enablethese capabilities on Ubuntu or Debian by following these instructions. Memoryand swap accounting incur an overhead of about 1% of the total available memoryand a 10% overall performance degradation, even if Docker is not running.

  1. Log into the Ubuntu or Debian host as a user with sudo privileges.

  2. Edit the /etc/default/grub file. Add or edit the GRUB_CMDLINE_LINUX lineto add the following two key-value pairs:

    Save and close the file.

  3. Update GRUB.

    If your GRUB configuration file has incorrect syntax, an error occurs.In this case, repeat steps 2 and 3.

    The changes take effect when the system is rebooted.

Next steps

Debian Start Docker Daemon

  • Take a look at the Get started training modules to learn how to build an image and run it as a containerized application.
  • Review the topics in Develop with Docker to learn how to build new applications using Docker.

Debian Start Docker Container On Boot

Docker, Docker documentation, requirements, apt, installation, ubuntu, install, uninstall, upgrade, update
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