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158 lines
5.3 KiB
Markdown
158 lines
5.3 KiB
Markdown
<!--[metadata]>
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+++
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title = "Control and configure Docker with systemd"
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description = "Controlling and configuring Docker using systemd"
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keywords = ["docker, daemon, systemd, configuration"]
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[menu.main]
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parent = "smn_administrate"
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weight = 7
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+++
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<![end-metadata]-->
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# Control and configure Docker with systemd
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Many Linux distributions use systemd to start the Docker daemon. This document
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shows a few examples of how to customise Docker's settings.
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## Starting the Docker daemon
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Once Docker is installed, you will need to start the Docker daemon.
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$ sudo systemctl start docker
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# or on older distributions, you may need to use
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$ sudo service docker start
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If you want Docker to start at boot, you should also:
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$ sudo systemctl enable docker
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# or on older distributions, you may need to use
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$ sudo chkconfig docker on
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## Custom Docker daemon options
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There are a number of ways to configure the daemon flags and environment variables
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for your Docker daemon.
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The recommended way is to use a systemd drop-in file. These are local files in
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the `/etc/systemd/system/docker.service.d` directory. This could also be
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`/etc/systemd/system/docker.service`, which also works for overriding the
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defaults from `/lib/systemd/system/docker.service`.
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However, if you had previously used a package which had an `EnvironmentFile`
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(often pointing to `/etc/sysconfig/docker`) then for backwards compatibility,
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you drop a file in the `/etc/systemd/system/docker.service.d`
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directory including the following:
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[Service]
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EnvironmentFile=-/etc/sysconfig/docker
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EnvironmentFile=-/etc/sysconfig/docker-storage
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EnvironmentFile=-/etc/sysconfig/docker-network
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ExecStart=
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ExecStart=/usr/bin/docker daemon -H fd:// $OPTIONS \
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$DOCKER_STORAGE_OPTIONS \
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$DOCKER_NETWORK_OPTIONS \
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$BLOCK_REGISTRY \
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$INSECURE_REGISTRY
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To check if the `docker.service` uses an `EnvironmentFile`:
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$ sudo systemctl show docker | grep EnvironmentFile
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EnvironmentFile=-/etc/sysconfig/docker (ignore_errors=yes)
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Alternatively, find out where the service file is located:
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$ sudo systemctl status docker | grep Loaded
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Loaded: loaded (/usr/lib/systemd/system/docker.service; enabled)
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$ sudo grep EnvironmentFile /usr/lib/systemd/system/docker.service
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EnvironmentFile=-/etc/sysconfig/docker
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You can customize the Docker daemon options using override files as explained in the
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[HTTP Proxy example](#http-proxy) below. The files located in `/usr/lib/systemd/system`
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or `/lib/systemd/system` contain the default options and should not be edited.
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### Runtime directory and storage driver
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You may want to control the disk space used for Docker images, containers
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and volumes by moving it to a separate partition.
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In this example, we'll assume that your `docker.service` file looks something like:
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[Unit]
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Description=Docker Application Container Engine
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Documentation=https://docs.docker.com
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After=network.target docker.socket
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Requires=docker.socket
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[Service]
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Type=notify
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ExecStart=/usr/bin/docker daemon -H fd://
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LimitNOFILE=1048576
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LimitNPROC=1048576
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[Install]
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Also=docker.socket
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This will allow us to add extra flags via a drop-in file (mentioned above) by
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placing a file containing the following in the `/etc/systemd/system/docker.service.d`
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directory:
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[Service]
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ExecStart=
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ExecStart=/usr/bin/docker daemon -H fd:// --graph /mnt/docker-data --storage-driver btrfs
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You can also set other environment variables in this file, for example, the
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`HTTP_PROXY` environment variables described below.
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To modify the ExecStart configuration, specify an empty configuration followed
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by a new configuration as follows:
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[Service]
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ExecStart=
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ExecStart=/usr/bin/docker daemon -H fd:// --bip=172.17.42.1/16
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If you fail to specify an empty configuration, Docker reports an error such as:
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docker.service has more than one ExecStart= setting, which is only allowed for Type=oneshot services. Refusing.
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### HTTP proxy
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This example overrides the default `docker.service` file.
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If you are behind a HTTP proxy server, for example in corporate settings,
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you will need to add this configuration in the Docker systemd service file.
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First, create a systemd drop-in directory for the docker service:
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mkdir /etc/systemd/system/docker.service.d
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Now create a file called `/etc/systemd/system/docker.service.d/http-proxy.conf`
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that adds the `HTTP_PROXY` environment variable:
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[Service]
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Environment="HTTP_PROXY=http://proxy.example.com:80/"
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If you have internal Docker registries that you need to contact without
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proxying you can specify them via the `NO_PROXY` environment variable:
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Environment="HTTP_PROXY=http://proxy.example.com:80/" "NO_PROXY=localhost,127.0.0.0/8,docker-registry.somecorporation.com"
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Flush changes:
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$ sudo systemctl daemon-reload
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Verify that the configuration has been loaded:
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$ sudo systemctl show docker --property Environment
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Environment=HTTP_PROXY=http://proxy.example.com:80/
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Restart Docker:
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$ sudo systemctl restart docker
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## Manually creating the systemd unit files
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When installing the binary without a package, you may want
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to integrate Docker with systemd. For this, simply install the two unit files
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(service and socket) from [the github
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repository](https://github.com/docker/docker/tree/master/contrib/init/systemd)
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to `/etc/systemd/system`.
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