: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.
      -w="": Working directory inside the container


Examples
--------

.. code-block:: bash

    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.

.. code-block:: bash

   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:

.. code-block:: bash

   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.

.. code-block:: bash

   docker  run -w /path/to/dir/ -i -t  ubuntu pwd

The ``-w`` lets the command beeing executed inside directory given, 
here /path/to/dir/. If the path does not exists it is created inside the 
container.

.. code-block:: bash

   docker  run  -v `pwd`:`pwd` -w `pwd` -i -t  ubuntu pwd

The ``-v`` flag mounts the current working directory into the container. 
The ``-w`` lets the command beeing executed inside the current 
working directory, by changeing into the directory to the value
returned by ``pwd``. So this combination executes the command
using the container, but inside the current working directory.