moby--moby/docs/sources/introduction/working-with-docker.md

page_title: Introduction to working with Docker page_description: Introduction to working with Docker and Docker commands. page_keywords: docker, introduction, documentation, about, technology, understanding, Dockerfile

An Introduction to working with Docker

Getting started with Docker

Note: If you would like to see how a specific command works, check out the glossary of all available client commands on our Commands Reference.

Introduction

In the Understanding Docker section we covered the components that make up Docker, learned about the underlying technology and saw how everything works.

Now, let's get an introduction to the basics of interacting with Docker.

Note: This page assumes you have a host with a running Docker daemon and access to a Docker client. To see how to install Docker on a variety of platforms see the installation section.

How to use the client

The client provides you a command-line interface to Docker. It is accessed by running the docker binary.

Tip: The below instructions can be considered a summary of our interactive tutorial. If you prefer a more hands-on approach without installing anything, why not give that a shot and check out the tutorial.

The docker client usage is pretty simple. Each action you can take with Docker is a command and each command can take a series of flags and arguments.

# Usage:  [sudo] docker [flags] [command] [arguments] ..
# Example:
$ docker run -i -t ubuntu /bin/bash

Using the Docker client

Let's get started with the Docker client by running our first Docker command. We're going to use the docker version command to return version information on the currently installed Docker client and daemon.

# Usage: [sudo] docker version
# Example:
$ docker version

This command will not only provide you the version of Docker client and daemon you are using, but also the version of Go (the programming language powering Docker).

Client version: 0.8.0
Go version (client): go1.2

Git commit (client): cc3a8c8
Server version: 0.8.0

Git commit (server): cc3a8c8
Go version (server): go1.2

Last stable version: 0.8.0

Seeing what the Docker client can do

We can see all of the commands available to us with the Docker client by running the docker binary without any options.

# Usage: [sudo] docker
# Example:
$ docker

You will see a list of all currently available commands.

Commands:
     attach    Attach to a running container
     build     Build an image from a Dockerfile
     commit    Create a new image from a container's changes
. . .

Seeing Docker command usage

You can also zoom in and review the usage for specific Docker commands.

Try typing Docker followed with a [command] to see the usage for that command:

# Usage: [sudo] docker [command] [--help]
# Example:
$ docker attach
Help output . . .

Or you can also pass the --help flag to the docker binary.

$ docker images --help

This will display the help text and all available flags:

Usage: docker attach [OPTIONS] CONTAINER

Attach to a running container

  --no-stdin=false: Do not attach stdin
  --sig-proxy=true: Proxify all received signal to the process (even in non-tty mode)

Working with images

Let's get started with using Docker by working with Docker images, the building blocks of Docker containers.

Docker Images

As we've discovered a Docker image is a read-only template that we build containers from. Every Docker container is launched from an image. You can use both images provided by Docker, such as the base ubuntu image, as well as images built by others. For example we can build an image that runs Apache and our own web application as a starting point to launch containers.

Searching for images

To search for Docker image we use the docker search command. The docker search command returns a list of all images that match your search criteria, together with some useful information about that image.

This information includes social metrics like how many other people like the image: we call these "likes" stars. We also tell you if an image is trusted. A trusted image is built from a known source and allows you to introspect in greater detail how the image is constructed.

# Usage: [sudo] docker search [image name]
# Example:
$ docker search nginx

NAME                               DESCRIPTION                                     STARS  OFFICIAL   TRUSTED
dockerfile/nginx                   Trusted Nginx (http://nginx.org/) Build         6                 [OK]
paintedfox/nginx-php5              A docker image for running Nginx with PHP5.     3                 [OK]
dockerfiles/django-uwsgi-nginx     Dockerfile and configuration files to buil...   2                 [OK]
. . .

Note: To learn more about trusted builds, check out this blog post.

Downloading an image

Once we find an image we'd like to download we can pull it down from Docker.io using the docker pull command.

# Usage: [sudo] docker pull [image name]
# Example:
$ docker pull dockerfile/nginx

Pulling repository dockerfile/nginx
0ade68db1d05: Pulling dependent layers
27cf78414709: Download complete
b750fe79269d: Download complete
. . .

As you can see, Docker will download, one by one, all the layers forming the image.

Listing available images

You may already have some images you've pulled down or built yourself and you can use the docker images command to see the images available to you locally.

# Usage: [sudo] docker images
# Example:
$ docker images

REPOSITORY          TAG                 IMAGE ID            CREATED             VIRTUAL SIZE
myUserName/nginx    latest              a0d6c70867d2        41 seconds ago      578.8 MB
nginx               latest              173c2dd28ab2        3 minutes ago       578.8 MB
dockerfile/nginx    latest              0ade68db1d05        3 weeks ago         578.8 MB

Building our own images

You can build your own images using a Dockerfile and the docker build command. The Dockerfile is very flexible and provides a powerful set of instructions for building applications into Docker images. To learn more about the Dockerfile see the Dockerfile Reference and tutorial.

Working with containers

Docker Containers

Docker containers run your applications and are built from Docker images. In order to create or start a container, you need an image. This could be the base ubuntu image or an image built and shared with you or an image you've built yourself.

Running a new container from an image

The easiest way to create a new container is to run one from an image using the docker run command.

# Usage: [sudo] docker run [arguments] ..
# Example:
$ docker run -d --name nginx_web nginx /usr/sbin/nginx
25137497b2749e226dd08f84a17e4b2be114ddf4ada04125f130ebfe0f1a03d3

This will create a new container from an image called nginx which will launch the command /usr/sbin/nginx when the container is run. We've also given our container a name, nginx_web. When the container is run Docker will return a container ID, a long string that uniquely identifies our container. We use can the container's name or its string to work with it.

Containers can be run in two modes:

• Interactive;
• Daemonized;

An interactive container runs in the foreground and you can connect to it and interact with it, for example sign into a shell on that container. A daemonized container runs in the background.

A container will run as long as the process you have launched inside it is running, for example if the /usr/bin/nginx process stops running the container will also stop.

Listing containers

We can see a list of all the containers on our host using the docker ps command. By default the docker ps command only shows running containers. But we can also add the -a flag to show all containers: both running and stopped.

# Usage: [sudo] docker ps [-a]
# Example:
$ docker ps

CONTAINER ID        IMAGE                     COMMAND             CREATED             STATUS              PORTS                NAMES
842a50a13032        $ dockerfile/nginx:latest   nginx               35 minutes ago      Up 30 minutes       0.0.0.0:80->80/tcp   nginx_web

Stopping a container

You can use the docker stop command to stop an active container. This will gracefully end the active process.

# Usage: [sudo] docker stop [container ID]
# Example:
$ docker stop nginx_web
nginx_web

If the docker stop command succeeds it will return the name of the container it has stopped.

Note: If you want you to more aggressively stop a container you can use the docker kill command.

Starting a Container

Stopped containers can be started again.

# Usage: [sudo] docker start [container ID]
# Example:
$ docker start nginx_web
nginx_web

If the docker start command succeeds it will return the name of the freshly started container.

Next steps

Here we've learned the basics of how to interact with Docker images and how to run and work with our first container.

Understanding Docker

Visit Understanding Docker.

Installing Docker

Visit the installation section.

Get the whole story

https://www.docker.io/the_whole_story/