Docker is a software for automating the deployment and management of applications in an operating system-level virtualization environment. It allows you to package an application with all its environment and dependencies into a container that can be ported to any Linux system with kernel cgroups support and provides a container management environment

    file

    Compose a tool for creating and running multi-container Docker applications. In Compose, you use a special file to configure your application services

    The features of Compose that make it effective are:

    • Multiple isolated environments on a single host
    • Protection of volume data when containers are created
    • Only changed containers are recreated
    • Moving variables between environments

    Before installing Docker Compose, make sure Docker is installed, see this manual for details on installation.

    Installing Docker Compose

    Let's install Docker Compose from the Docker repository on GitHub. The following syntax avoids the unauthorized error that occurs when using sudo.

    Let's check current version and update it if necessary using the following command:

    sudo curl -L https://github.com/docker/compose/releases/download/1.25.5/docker-compose-`uname -s`-`uname -m` -o /usr/local/bin/docker-compose  
    
    [email protected]:~# sudo curl -L https://github.com/docker/compose/releases/download/1.25.5/docker-compose-`uname -s`-`uname -m` -o /usr/local/bin/docker-compose  
      % Total % Received % Xferd Average Speed Time Time Time Current
                                     Dload Upload Total Spent Left Speed
    100   638  100   638    0     0    979      0 --:--:-- --:--:-- --:--:--   980  
    100 16.7M 100 16.7M 0 0 1198k 0 0:00:14 0:00:14 --:--:--:2471k  
    

    Next, we'll set up the permissions:

    sudo chmod +x /usr/local/bin/docker-compose  
    

    Then we will check that the installation was successful:

    docker-compose --version  
    

    You will see a similar output:

    [email protected]:~# docker-compose --version  
    docker-compose version 1.25.5, build 8a1c60f6  
    

    Starting the container with Docker Compose

    The Docker registry, Docker Hub, contains a Hello World image used for demonstration and testing. It demonstrates the minimum configuration parameters needed to start a container using Docker Compose: a YAML file calling a separate image:

    Create a directory for the YAML file:

    mkdir hello-world  
    

    Let's go into it:

    cd hello-world  
    

    Next, create a YAML file in that directory:

    nano docker-compose.yml  
    

    Put the following data into the file, save it, and close the text editor:

    my-test:  
     image: hello-world
    

    The first line of the YAML file is used as part of the container name
    The second line specifies which image is used to create the container
    When you run the docker-compose up command, it will search for the local image by the specified name, i.e. hello-world.

    Next, you can view the images on our system using the docker images command:

    docker images  
    

    When there are no local images, only the column headers will be displayed:

    REPOSITORY TAG IMAGE ID CREATED SIZE  
    

    Next, while in the ~/hello-world directory, we run the following command:

    docker-compose up  
    

    After loading the image, docker-compose creates a container, puts it in, and runs the hello program:

    [email protected]:~/hello-world# docker-compose up  
    Creating hello-world_my-test_1 ... done  
    Attaching to hello-world_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 |  
    my-test_1 | 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  
    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.  
    my-test_1 |  
    my-test_1_1 | To try something more ambitious, you can run an Ubuntu container with:  
    my-test_1 | $ docker run -it ubuntu bash  
    my-test_1 |  
    my-test_1 | Share images, automate workflows, and more with a free Docker ID:  
    my-test_1 | https://hub.docker.com/  
    my-test_1 |  
    my-test_1 | For more examples and ideas, visit:  
    my-test_1 | https://docs.docker.com/get-started/  
    my-test_1 |  
    hello-world_my-test_1 exited with code 0  
    

    Docker containers continue to run as long as the command remains active, so when the hello container finishes, it stops. Consequently, when we view active processes, the column headers will appear, but the hello-world container will not appear in the list because it is not running.

    docker ps  
    
    CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES  
    

    We can view the container information by using the -a flag to display all containers, not just the active ones:

    docker ps -a  
    
    [email protected]:~/hello-world# docker ps -a  
    CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES  
    4e8158d490ac hello-world "/hello" 7 minutes ago Exited (0) 7 minutes ago hello-world_my-test_1