Docker run
External
- https://docs.docker.com/engine/reference/commandline/run/
- https://docs.docker.com/engine/reference/run/
Internal
Overview
Without any arguments except the name of image, it creates a new container based on the given image, and executes it in the foreground, connecting the current terminal's stdin/stdout/stderr to the container:
docker run novaordis/centos-loop
The docker runtime will first attempt to use an image from the local registry, and if it does find it, it will attempt to pull it from Docker Hub and then cache locally in the local registry.
In order to run the container in the background, use -d | --detach.
The generic format of the command is:
docker run [options] <image> [command] [args...]
Example:
docker run -d --name="runloop1" -e SOME_ENV_VAR="some value" \
busybox \
/bin/sh -c 'i=0; while true; do echo ${i}; i=$(expr ${i} + 1); sleep 1s; done'
A running container, either in foreground or background, can be with listed with:
docker ps
it can be stopped with:
docker stop
and then it can be restarted with:
docker start
Anything that a running container sends to stdout can be explored with docker logs.
More container operations:
The Run Process
Once the "run" command is executed, the following sequence takes place:
- The Docker runtime creates a set of namespaces and control groups for the container.
- TODO
Options
-d, --detach
Run the container in the background and print the container ID.
-e, --env
-e SOME_ENV_VAR="some value"
Set environment variables.
--name
Assign a name to the container, otherwise the name will be assigned automatically to something like "pedantic_einstein" or "competent_aryabhata".
--name="bluebox"
--restart
Configures the restart policy of the container being created.
--restart=always
See:
-p, --publish
-p|--publish list
Publish a container's port(s) to the host. Also see Dockerfile EXPOSE.
To publish port 8080:
docker run ... -p 8080:8080/tcp ...
-P, --publish-all
Publish all exposed ports to random ports. Also see Dockerfile EXPOSE.
-v, --volume
... -v <native-host-path>:<container-mount-point> ...
--mount is recommended instead.
See:
--mount
See:
--storage-opt list
Storage driver options for the container. Controls the following:
Base Device Size
The amount of storage allocated to the container when the image is run (this was only tested with device-mapper):
... --storage-opt size=20G ...
This value cannot be smaller than the default value, see device-mapper Base Device Size.
Resource Management Options
-m, --memory
The memory limit, in bytes. Apparently, that means the same amount will be allowed for "RAM" and swap, so a process can use double the specified amount, if it starts swapping. Also see Resource Management.
--rm
Automatically remove the container when it exits.
Mounting Data Volumes
If the container has volume mount points specified with VOLUME in its original Dockerfile, those mount points must be bound to paths on the native host when the container is created. This is done with --v|--volume or --mount (recommended) command line options, as follows:
docker run ... --mount type=bind,src=<native-host-path>,dst=<container-mount-point> ...
docker run ... --mount type=bind,src=/data-volumes/postgresql,dst=/var/lib/pgsql/data ...
When --mount with type=bind is used, the native-host-path must refer to an existing path on the host. The path will not be created if it does not exist, and the command will fail. Also, the mount point must have sufficient permissions. For more details on native host path permissions, see Native Host Path Permissions.
Troubleshooting
User has No Appropriate Permissions
The attempt to run the ps or run command under a user that has no appropriate permissions leads to:
Cannot connect to the Docker daemon. Is the docker daemon running on this host?