Check the current release and, if necessary, update it in the command that follows:
sudo curl -L https://github.com/docker/compose/releases/download/1.25.3/docker-compose-`uname -s`-`uname -m` -o /usr/local/bin/docker-compose
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Next we’ll set the permissions:
sudo chmod +x /usr/local/bin/docker-compose
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Then we’ll verify that the installation was successful by checking the version:
docker-compose --version
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This will print out the version we installed:
Outputdocker-compose version 1.25.3, build d4d1b42b
Now that we have Docker Compose installed, we’re ready to run a “Hello World” example.
Step 2 — Running a Container with Docker Compose
The public Docker registry, Docker Hub, includes a Hello World image for demonstration and testing. It illustrates the minimal configuration required to run a container using Docker Compose: a YAML file that calls a single image. We’ll create this minimal configuration to run our hello-world container.
First, create a directory for the YAML file and switch to it:
mkdir hello-world
cd hello-world
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Then create the YAML file:
nano docker-compose.yml
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Put the following contents into the file, save the file, and exit the text editor:
docker-compose.yml
my-test:
image: hello-world
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The first line in the YAML file is used as part of the container name. The second line specifies which image to use to create the container. When we run the docker-compose up command, it will look for a local image by the name we specified, hello-world. With this in place, we’ll save and exit the file.
You can look manually at images on our system with the docker images command:
docker images
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When there are no local images at all, only the column headings display:
OutputREPOSITORY TAG IMAGE ID CREATED SIZE
Now, while still in the ~/hello-world directory, execute the following command:
docker-compose up
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The first time you run the command, if there’s no local image named hello-world, Docker Compose will pull it from the Docker Hub public repository:
OutputPulling my-test (hello-world:)...
latest: Pulling from library/hello-world
9db2ca6ccae0: Pull complete
Digest: sha256:4b8ff392a12ed9ea17784bd3c9a8b1fa3299cac44aca35a85c90c5e3c7afacdc
Status: Downloaded newer image for hello-world:latest
. . .
After pulling the image, docker-compose creates a container, attaches, and runs the hello program, which in turn confirms that the installation appears to be working:
Output. . .
Creating helloworld_my-test_1...
Attaching to helloworld_my-test_1
my-test_1 |
my-test_1 | Hello from Docker.
my-test_1 | This message shows that your installation appears to be working correctly.
my-test_1 |
. . .
Then it prints an explanation of what it did:
Output To generate this message, Docker took the following steps:
my-test_1 | 1. The Docker client contacted the Docker daemon.
my-test_1 | 2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
my-test_1 | (amd64)
my-test_1 | 3. The Docker daemon created a new container from that image which runs the
my-test_1 | executable that produces the output you are currently reading.
my-test_1 | 4. The Docker daemon streamed that output to the Docker client, which sent it
my-test_1 | to your terminal.
Docker containers only run as long as the command is active, so once hello finished running, the container stopped. Consequently, when we look at active processes, the column headers will appear, but the hello-world container won’t be listed because it’s not running:
docker ps
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OutputCONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
You can see the container information, which you’ll need in the next step, by using the -a flag. This shows all containers, not just active ones:
docker ps -a
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OutputCONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
06069fd5ca23 hello-world "/hello" 35 minutes ago Exited (0) 35 minutes ago hello-world_my-test_1
This displays the information you’ll need to remove the container when you’re done with it.
Step 3 — Removing the Image (Optional)
To avoid using unnecessary disk space, we’ll remove the local image. To do so, we’ll need to delete all the containers that reference the image using the docker rm command, followed by either the CONTAINER ID or the NAME. In the following example, we’re using the CONTAINER ID from the docker ps -a command we just ran. Be sure to substitute the ID of your container:
docker rm 06069fd5ca23
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Once all containers that reference the image have been removed, we can remove the image:
docker rmi hello-world