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If you run the tutorial step-by-step, following error occurs: ```$ sudo docker logs $container_id Usage: docker logs CONTAINER Fetch the logs of a container -f, --follow=false: Follow log output``` This is obviously because bash variables are case-sensitive, so it mustn't be `CONTAINER_ID` above. Docker-DCO-1.1-Signed-off-by: Mateusz Sulima <sulima.mateusz@email.com> (github: github_handle)
162 lines
5.9 KiB
Markdown
162 lines
5.9 KiB
Markdown
page_title: Hello world example
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page_description: A simple hello world example with Docker
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page_keywords: docker, example, hello world
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# Check your Docker installation
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This guide assumes you have a working installation of Docker. To check
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your Docker install, run the following command:
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# Check that you have a working install
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$ sudo docker info
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If you get `docker: command not found` or something
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like `/var/lib/docker/repositories: permission denied`
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you may have an incomplete Docker installation or insufficient
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privileges to access docker on your machine.
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Please refer to [*Installation*](/installation/)
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for installation instructions.
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## Hello World
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> **Note**:
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>
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> - This example assumes you have Docker running in daemon mode. For
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> more information please see [*Check your Docker
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> install*](#check-your-docker-installation).
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> - **If you don't like sudo** then see [*Giving non-root
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> access*](/installation/binaries/#dockergroup)
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This is the most basic example available for using Docker.
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Download the small base image named `busybox`:
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# Download a busybox image
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$ sudo docker pull busybox
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The `busybox` image is a minimal Linux system. You can do the same with
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any number of other images, such as `debian`, `ubuntu` or `centos`. The
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images can be found and retrieved using the
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[Docker.io](http://index.docker.io) registry.
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$ sudo docker run busybox /bin/echo hello world
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This command will run a simple `echo` command, that
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will echo `hello world` back to the console over
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standard out.
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**Explanation:**
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- **"sudo"** execute the following commands as user *root*
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- **"docker run"** run a command in a new container
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- **"busybox"** is the image we are running the command in.
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- **"/bin/echo"** is the command we want to run in the container
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- **"hello world"** is the input for the echo command
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**Video:**
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See the example in action
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<iframe width="640" height="480" frameborder="0" sandbox="allow-same-origin allow-scripts" srcdoc="<body><script type="text/javascript"src="https://asciinema.org/a/7658.js"id="asciicast-7658" async></script></body>"></iframe>
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<iframe width="640" height="480" frameborder="0" sandbox="allow-same-origin allow-scripts" srcdoc="<body><script type="text/javascript"src="https://asciinema.org/a/7658.js"id="asciicast-7658" async></script></body>"></iframe>
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## Hello World Daemon
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> **Note**:
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>
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> - This example assumes you have Docker running in daemon mode. For
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> more information please see [*Check your Docker
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> install*](#check-your-docker-installation).
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> - **If you don't like sudo** then see [*Giving non-root
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> access*](/installation/binaries/#dockergroup)
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And now for the most boring daemon ever written!
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We will use the Ubuntu image to run a simple hello world daemon that
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will just print hello world to standard out every second. It will
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continue to do this until we stop it.
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**Steps:**
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$ container_id=$(sudo docker run -d ubuntu /bin/sh -c "while true; do echo hello world; sleep 1; done")
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We are going to run a simple hello world daemon in a new container made
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from the `ubuntu` image.
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- **"sudo docker run -d "** run a command in a new container. We pass
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"-d" so it runs as a daemon.
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- **"ubuntu"** is the image we want to run the command inside of.
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- **"/bin/sh -c"** is the command we want to run in the container
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- **"while true; do echo hello world; sleep 1; done"** is the mini
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script we want to run, that will just print hello world once a
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second until we stop it.
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- **$container_id** the output of the run command will return a
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container id, we can use in future commands to see what is going on
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with this process.
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<!-- -->
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$ sudo docker logs $container_id
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Check the logs make sure it is working correctly.
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- **"docker logs**" This will return the logs for a container
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- **$container_id** The Id of the container we want the logs for.
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<!-- -->
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$ sudo docker attach --sig-proxy=false $container_id
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Attach to the container to see the results in real-time.
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- **"docker attach**" This will allow us to attach to a background
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process to see what is going on.
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- **"–sig-proxy=false"** Do not forward signals to the container;
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allows us to exit the attachment using Control-C without stopping
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the container.
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- **$container_id** The Id of the container we want to attach to.
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Exit from the container attachment by pressing Control-C.
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$ sudo docker ps
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Check the process list to make sure it is running.
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- **"docker ps"** this shows all running process managed by docker
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<!-- -->
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$ sudo docker stop $container_id
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Stop the container, since we don't need it anymore.
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- **"docker stop"** This stops a container
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- **$container_id** The Id of the container we want to stop.
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<!-- -->
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$ sudo docker ps
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Make sure it is really stopped.
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**Video:**
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See the example in action
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<iframe width="640" height="480" frameborder="0" sandbox="allow-same-origin allow-scripts" srcdoc="<body><script type="text/javascript"src="https://asciinema.org/a/2562.js"id="asciicast-2562" async></script></body>"></iframe>
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<iframe width="640" height="480" frameborder="0" sandbox="allow-same-origin allow-scripts" srcdoc="<body><script type="text/javascript"src="https://asciinema.org/a/2562.js"id="asciicast-2562" async></script></body>"></iframe>
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The next example in the series is a [*Node.js Web App*](
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../nodejs_web_app/#nodejs-web-app) example, or you could skip to any of the
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other examples:
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- [*Node.js Web App*](../nodejs_web_app/#nodejs-web-app)
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- [*Redis Service*](../running_redis_service/#running-redis-service)
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- [*SSH Daemon Service*](../running_ssh_service/#running-ssh-service)
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- [*CouchDB Service*](../couchdb_data_volumes/#running-couchdb-service)
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- [*PostgreSQL Service*](../postgresql_service/#postgresql-service)
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- [*Building an Image with MongoDB*](../mongodb/#mongodb-image)
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- [*Python Web App*](../python_web_app/#python-web-app)
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