Wednesday, September 28, 2016

Install Docker in RHEL/CentOS 7

Docker is supported on Red Hat Enterprise Linux 7. Docker requires a 64-bit installation regardless of your Red Hat version. Docker requires that your kernel must be 3.10 at minimum, which Red Hat 7 runs.

Install with yum

  1. Log into your machine as a user with sudo or root privileges.
  2. Make sure your existing yum packages are up-to-date.
    $ sudo yum update
  3. Add the yum repo yourself.
    $ sudo tee /etc/yum.repos.d/docker.repo <<-EOF
    name=Docker Repository
  4. Install the Docker package.
    $ sudo yum install docker-engine 
  5. If you are getting ' Public key not installed' error try installing like below
  6. yum install --nogpgcheck docker-engine

  • Start the Docker daemon.

  1. $ sudo service docker start
    $ sudo systemctl start docker.service
  2. Verify docker is installed correctly by running a test image in a container.
  3. $ sudo docker run hello-world
    Unable to find image 'hello-world:latest' locally
        latest: Pulling from hello-world
        a8219747be10: Pull complete
        91c95931e552: Already exists
        hello-world:latest: The image you are pulling has been verified. Important: image verification is a tech preview feature and should not be relied on to provide security.
        Digest: sha256:aa03e5d0d5553b4c3473e89c8619cf79df368babd1.7.1cf5daeb82aab55838d
        Status: Downloaded newer image for hello-world:latest
        Hello from Docker.
        This message shows that your installation appears to be working correctly.
        To generate this message, Docker took the following steps:
         1. The Docker client contacted the Docker daemon.
         2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
                (Assuming it was not already locally available.)
         3. The Docker daemon created a new container from that image which runs the
                executable that produces the output you are currently reading.
         4. The Docker daemon streamed that output to the Docker client, which sent it
                to your terminal.
        To try something more ambitious, you can run an Ubuntu container with:
         $ docker run -it ubuntu bash
        For more examples and ideas, visit:
  4. Create a docker group

    The docker daemon binds to a Unix socket instead of a TCP port. By default that Unix socket is owned by the user root and other users can access it with sudo. For this reason, docker daemon always runs as the rootuser.
    To avoid having to use sudo when you use the docker command, create a Unix group called docker and add users to it. When the docker daemon starts, it makes the ownership of the Unix socket read/writable by thedocker group.
    Warning: The docker group is equivalent to the root user; For details on how this impacts security in your system, see Docker Daemon Attack Surface for details.
    To create the docker group and add your user:
    1. Log into your machine as a user with sudo or root privileges.
    2. Create the docker group.
      sudo groupadd docker
    3. Add your user to docker group.
      sudo usermod -aG docker your_username
    4. Log out and log back in.
      This ensures your user is running with the correct permissions.
    5. Verify your work by running docker without sudo.
          $ docker run hello-world

    Start the docker daemon at boot

    To ensure Docker starts when you boot your system, do the following:
    $ sudo chkconfig docker on
    If you need to add an HTTP Proxy, set a different directory or partition for the Docker runtime files, or make other customizations, read our Systemd article to learn how to customize your Systemd Docker daemon options.


    You can uninstall the Docker software with yum.
    1. List the package you have installed.
      $ yum list installed | grep docker
      yum list installed | grep docker
      docker-engine.x86_64                1.7.1-0.1.el7@/docker-engine-1.7.1-0.1.el7.x86_64
    2. Remove the package.
      $ sudo yum -y remove docker-engine.x86_64
      This command does not remove images, containers, volumes, or user created configuration files on your host.
    3. To delete all images, containers, and volumes run the following command:
      $ rm -rf /var/lib/docker
    4. Locate and delete any user-created configuration files.

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