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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
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
Additionally, depending on your Docker system configuration, you may be required
to preface each docker
command with sudo
. To avoid having to use sudo
with
the docker
command, your system administrator can create a Unix group called
docker
and add users to it.
For more information about installing Docker or sudo
configuration, refer to
the installation instructions for your operating system.
Download a pre-built image
# Download an ubuntu image
$ docker pull ubuntu
This will find the ubuntu
image by name on
Docker Hub
and download it from Docker Hub 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 usingdocker inspect
ordocker images --no-trunc=true
{{ include "no-remote-sudo.md" }}
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")
$ 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 todocker
. 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 0.0.0.0:2375
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:2375
-> TCP connection on host:2375unix://path/to/socket
-> Unix socket located atpath/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:
$ 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://127.0.0.1:2375 -H unix:///var/run/docker.sock -d &
# Download an ubuntu image, use default Unix socket
$ docker pull ubuntu
# OR use the TCP port
$ docker -H tcp://127.0.0.1:2375 pull ubuntu
Starting a long-running worker process
# Start a very useful long-running process
$ JOB=$(docker run -d ubuntu /bin/sh -c "while true; do echo Hello world; sleep 1; done")
# Collect the output of the job so far
$ docker logs $JOB
# Kill the job
$ docker kill $JOB
Listing containers
$ docker ps # Lists only running containers
$ docker ps -a # Lists all containers
Controlling containers
# Start a new container
$ JOB=$(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=$(docker run -d -p 4444 ubuntu:12.10 /bin/nc -l 4444)
# Which public port is NATed to my container?
$ PORT=$(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: $(docker logs $JOB)"
Committing (saving) a container state
Save your containers state to an 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
$ docker commit <container_id> <some_name>
# List your containers
$ docker images
You now have an image state from which you can create new instances.
Read more about Share Images via Repositories or continue to the complete Command Line