cli/components/engine/docs/sources/commandline/command/run.rst

title

Run Command

description

Run a command in a new container

keywords

run, container, docker, documentation

run -- Run a command in a new container

Usage: docker run [OPTIONS] IMAGE[:TAG] [COMMAND] [ARG...]

Run a command in a new container

  -a=map[]: Attach to stdin, stdout or stderr.
  -c=0: CPU shares (relative weight)
  -cidfile="": Write the container ID to the file
  -d=false: Detached mode: Run container in the background, print new container id
  -e=[]: Set environment variables
  -h="": Container host name
  -i=false: Keep stdin open even if not attached
  -privileged=false: Give extended privileges to this container
  -m=0: Memory limit (in bytes)
  -n=true: Enable networking for this container
  -p=[]: Map a network port to the container
  -t=false: Allocate a pseudo-tty
  -u="": Username or UID
  -dns=[]: Set custom dns servers for the container
  -v=[]: Create a bind mount with: [host-dir]:[container-dir]:[rw|ro]. If "host-dir" is missing, then docker creates a new volume.
  -volumes-from="": Mount all volumes from the given container.
  -entrypoint="": Overwrite the default entrypoint set by the image.

Examples

sudo docker run -cidfile /tmp/docker_test.cid ubuntu echo "test"

This will create a container and print "test" to the console. The cidfile flag makes docker attempt to create a new file and write the container ID to it. If the file exists already, docker will return an error. Docker will close this file when docker run exits.

docker run mount -t tmpfs none /var/spool/squid

This will not work, because by default, most potentially dangerous kernel capabilities are dropped; including cap_sys_admin (which is required to mount filesystems). However, the -privileged flag will allow it to run:

docker run -privileged mount -t tmpfs none /var/spool/squid

The -privileged flag gives all capabilities to the container, and it also lifts all the limitations enforced by the device cgroup controller. In other words, the container can then do almost everything that the host can do. This flag exists to allow special use-cases, like running Docker within Docker.