page_title: First steps with Docker
page_description: Common usage and commands
page_keywords: Examples, Usage, basic commands, docker, documentation, examples

# First steps with Docker

## Check your Docker install

This guide assumes you have a working installation of Docker. To check
your Docker install, run the following command:

    # Check that you have a working install
    docker info

If you get `docker: command not found` or something
like `/var/lib/docker/repositories: permission denied`
you may have an incomplete docker installation or insufficient
privileges to access Docker on your machine.

Please refer to [*Installation*](../../installation/#installation-list)
for installation instructions.

## Download a pre-built image

    # Download an ubuntu image
    sudo docker pull ubuntu

This will find the `ubuntu` image by name in the
[*Central Index*](../workingwithrepository/#searching-central-index) and
download it from the top-level Central Repository to a local image
cache.

Note

When the image has successfully downloaded, you will see a 12 character
hash `539c0211cd76: Download complete` which is the
short form of the image ID. These short image IDs are the first 12
characters of the full image ID - which can be found using
`docker inspect` or
`docker images --no-trunc=true`

**If you’re using OS X** then you shouldn’t use `sudo`.

## Running an interactive shell

    # Run an interactive shell in the ubuntu image,
    # allocate a tty, attach stdin and stdout
    # To detach the tty without exiting the shell,
    # use the escape sequence Ctrl-p + Ctrl-q
    # note: This will continue to exist in a stopped state once exited (see "docker ps -a")
    sudo docker run -i -t ubuntu /bin/bash

## Bind Docker to another host/port or a Unix socket

Warning

Changing the default `docker` daemon binding to a
TCP port or Unix *docker* user group will increase your security risks
by allowing non-root users to gain *root* access on the host. Make sure
you control access to `docker`. If you are binding
to a TCP port, anyone with access to that port has full Docker access;
so it is not advisable on an open network.

With `-H` it is possible to make the Docker daemon
to listen on a specific IP and port. By default, it will listen on
`unix:///var/run/docker.sock` to allow only local
connections by the *root* user. You *could* set it to
`0.0.0.0:4243` or a specific host IP to give access
to everybody, but that is **not recommended** because then it is trivial
for someone to gain root access to the host where the daemon is running.

Similarly, the Docker client can use `-H` to connect
to a custom port.

`-H` accepts host and port assignment in the
following format: `tcp://[host][:port]` or
`unix://path`

For example:

-   `tcp://host:4243` -\> tcp connection on
    host:4243
-   `unix://path/to/socket` -\> unix socket located
    at `path/to/socket`

`-H`, when empty, will default to the same value as
when no `-H` was passed in.

`-H` also accepts short form for TCP bindings:
`host[:port]` or `:port`

    # Run docker in daemon mode
    sudo <path to>/docker -H 0.0.0.0:5555 -d &
    # Download an ubuntu image
    sudo docker -H :5555 pull ubuntu

You can use multiple `-H`, for example, if you want
to listen on both TCP and a Unix socket

    # Run docker in daemon mode
    sudo <path to>/docker -H tcp://127.0.0.1:4243 -H unix:///var/run/docker.sock -d &
    # Download an ubuntu image, use default Unix socket
    sudo docker pull ubuntu
    # OR use the TCP port
    sudo docker -H tcp://127.0.0.1:4243 pull ubuntu

## Starting a long-running worker process

    # Start a very useful long-running process
    JOB=$(sudo docker run -d ubuntu /bin/sh -c "while true; do echo Hello world; sleep 1; done")

    # Collect the output of the job so far
    sudo docker logs $JOB

    # Kill the job
    sudo docker kill $JOB

## Listing containers

    sudo docker ps # Lists only running containers
    sudo docker ps -a # Lists all containers

## Controlling containers

    # Start a new container
    JOB=$(sudo docker run -d ubuntu /bin/sh -c "while true; do echo Hello world; sleep 1; done")

    # Stop the container
    docker stop $JOB

    # Start the container
    docker start $JOB

    # Restart the container
    docker restart $JOB

    # SIGKILL a container
    docker kill $JOB

    # Remove a container
    docker stop $JOB # Container must be stopped to remove it
    docker rm $JOB

## Bind a service on a TCP port

    # Bind port 4444 of this container, and tell netcat to listen on it
    JOB=$(sudo docker run -d -p 4444 ubuntu:12.10 /bin/nc -l 4444)

    # Which public port is NATed to my container?
    PORT=$(sudo docker port $JOB 4444 | awk -F: '{ print $2 }')

    # Connect to the public port
    echo hello world | nc 127.0.0.1 $PORT

    # Verify that the network connection worked
    echo "Daemon received: $(sudo docker logs $JOB)"

## Committing (saving) a container state

Save your containers state to a container image, so the state can be
re-used.

When you commit your container only the differences between the image
the container was created from and the current state of the container
will be stored (as a diff). See which images you already have using the
`docker images` command.

    # Commit your container to a new named image
    sudo docker commit <container_id> <some_name>

    # List your containers
    sudo docker images

You now have a image state from which you can create new instances.

Read more about [*Share Images via
Repositories*](../workingwithrepository/#working-with-the-repository) or
continue to the complete [*Command
Line*](../../reference/commandline/cli/#cli)