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93 lines
3.1 KiB
Markdown
93 lines
3.1 KiB
Markdown
<!--[metadata]>
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+++
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title = "Automatically start containers"
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description = "How to generate scripts for upstart, systemd, etc."
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keywords = ["systemd, upstart, supervisor, docker, documentation, host integration"]
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[menu.main]
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parent = "smn_containers"
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weight = 99
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+++
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<![end-metadata]-->
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# Automatically start containers
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As of Docker 1.2,
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[restart policies](/reference/run/#restart-policies-restart) are the
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built-in Docker mechanism for restarting containers when they exit. If set,
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restart policies will be used when the Docker daemon starts up, as typically
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happens after a system boot. Restart policies will ensure that linked containers
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are started in the correct order.
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If restart policies don't suit your needs (i.e., you have non-Docker processes
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that depend on Docker containers), you can use a process manager like
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[upstart](http://upstart.ubuntu.com/),
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[systemd](http://freedesktop.org/wiki/Software/systemd/) or
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[supervisor](http://supervisord.org/) instead.
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## Using a process manager
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Docker does not set any restart policies by default, but be aware that they will
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conflict with most process managers. So don't set restart policies if you are
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using a process manager.
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*Note:* Prior to Docker 1.2, restarting of Docker containers had to be
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explicitly disabled. Refer to the
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[previous version](/v1.1/articles/host_integration/) of this article for the
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details on how to do that.
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When you have finished setting up your image and are happy with your
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running container, you can then attach a process manager to manage it.
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When you run `docker start -a`, Docker will automatically attach to the
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running container, or start it if needed and forward all signals so that
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the process manager can detect when a container stops and correctly
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restart it.
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Here are a few sample scripts for systemd and upstart to integrate with
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Docker.
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## Examples
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The examples below show configuration files for two popular process managers,
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upstart and systemd. In these examples, we'll assume that we have already
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created a container to run Redis with `--name=redis_server`. These files define
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a new service that will be started after the docker daemon service has started.
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### upstart
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description "Redis container"
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author "Me"
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start on filesystem and started docker
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stop on runlevel [!2345]
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respawn
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script
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/usr/bin/docker start -a redis_server
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end script
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### systemd
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[Unit]
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Description=Redis container
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Requires=docker.service
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After=docker.service
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[Service]
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Restart=always
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ExecStart=/usr/bin/docker start -a redis_server
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ExecStop=/usr/bin/docker stop -t 2 redis_server
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[Install]
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WantedBy=local.target
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If you need to pass options to the redis container (such as `--env`),
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then you'll need to use `docker run` rather than `docker start`. This will
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create a new container every time the service is started, which will be stopped
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and removed when the service is stopped.
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[Service]
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...
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ExecStart=/usr/bin/docker run --env foo=bar --name redis_server redis
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ExecStop=/usr/bin/docker stop -t 2 redis_server ; /usr/bin/docker rm -f redis_server
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...
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