How to Install Docker on CentOS 7

Prerequisites:

• For the purposes of this tutorial, we will use a CentOS 7 VPS.
• Full SSH root access, or a user with sudo privileges is also required.

Step 1: Connect via SSH

Connect to your server via SSH as the root user using the following command:

ssh root@IP_ADDRESS -p PORT_NUMBER

and replace “IP_ADDRESS” and “PORT_NUMBER” with your actual server IP address and SSH port number.

Before starting with the installation, you will need to update your system packages to their latest versions.

You can do this by running the following command:

sudo yum update

Once the update is completed, we can move onto the installation step.

Step 2: Install Docker on CentOS 7

The recommended way to install Docker is to install from the Docker repositories. We will install some required dependencies with the following command:

sudo yum install yum-utils device-mapper-persistent-data lvm2

Next, we will add the Docker repository, enable it, and install it with the following commands:

sudo yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
sudo yum install docker-ce

After the installation has completed, we will start the Docker daemon:

sudo systemctl start docker

We can verify that it’s running with the following command:

sudo systemctl status docker

The output should be similar to the following:

 docker.service - Docker Application Container Engine
       Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
       Active: active (running) 
             Docs: https://docs.docker.com
Main PID: 4234 (dockerd)
       Tasks: 8
    CGroup: /system.slice/docker.service
                    └─4234 /usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock

Docker has now been successfully installed. In the next steps, we will show you how to use the docker command.

Step 3: Using the Docker Command

The syntax of the Docker CLI command takes this form:

docker [option] [command] [arguments]

To list all available commands, we need to run the docker command with no parameters:

docker

The output should be similar to the following:

A self-sufficient runtime for containers

Options:
--config string Location of client config files (default "/root/.docker")
-D, --debug Enable debug mode
-H, --host list Daemon socket(s) to connect to
-l, --log-level string Set the logging level ("debug"|"info"|"warn"|"error"|"fatal") (default "info")
--tls Use TLS; implied by --tlsverify
--tlscacert string Trust certs signed only by this CA (default "/root/.docker/ca.pem")
--tlscert string Path to TLS certificate file (default "/root/.docker/cert.pem")
--tlskey string Path to TLS key file (default "/root/.docker/key.pem")
--tlsverify Use TLS and verify the remote
-v, --version Print version information and quit

Management Commands:
builder     Manage builds
config      Manage Docker configs
container   Manage containers
engine      Manage the docker engine
image       Manage images
network     Manage networks
node        Manage Swarm nodes
plugin      Manage plugins
secret      Manage Docker secrets
service     Manage services
stack       Manage Docker stacks
swarm       Manage Swarm
system      Manage Docker
trust       Manage trust on Docker images
volume      Manage volumes

Commands:
  attach      Attach local standard input, output, and error streams to a running container
  build       Build an image from a Dockerfile
  commit      Create a new image from a container's changes
  cp          Copy files/folders between a container and the local filesystem
  create      Create a new container
  diff        Inspect changes to files or directories on a container's filesystem
  events      Get real time events from the server
  exec        Run a command in a running container
  export      Export a container's filesystem as a tar archive
  history     Show the history of an image
  images      List images
  import      Import the contents from a tarball to create a filesystem image
  info        Display system-wide information
  inspect     Return low-level information on Docker objects
  kill        Kill one or more running containers
  load        Load an image from a tar archive or STDIN
  login       Log in to a Docker registry
  logout      Log out from a Docker registry
  logs        Fetch the logs of a container
  pause       Pause all processes within one or more containers
  port        List port mappings or a specific mapping for the container
  ps          List containers
  pull        Pull an image or a repository from a registry
  push        Push an image or a repository to a registry
  rename      Rename a container
  restart     Restart one or more containers
  rm          Remove one or more containers
  rmi         Remove one or more images
  run         Run a command in a new container
  save        Save one or more images to a tar archive (streamed to STDOUT by default)
  search      Search the Docker Hub for images
  start       Start one or more stopped containers
  stats       Display a live stream of container(s) resource usage statistics
  stop        Stop one or more running containers
  tag         Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE
  top         Display the running processes of a container
  unpause     Unpause all processes within one or more containers
  update      Update configuration of one or more containers
  version     Show the Docker version information
  wait        Block until one or more containers stop, then print their exit codes

To see the options available to a specific command, execute the following command:

docker docker-subcommand --help

To view information about Docker:

docker info

Step 4: The Docker Command Line Interface

To search for an image from the Docker Hub registry, we can use the following command:

docker search centos

If you want to download an official copy of CentOS 7, we can do this by using the image pull subcommand:

docker image pull centos

If there is no tag specified, Docker will pull the latest image.

We can list the images by using the following command:

docker image ls

If you need to remove an image for any reason, you can use the following command:

docker image rm centos

To start, stop, remove, and manage a container, you can do this with the following subcommand:

docker container

With the following command, we can start a Docker container:

docker container run centos

If you need to interact with the container via the command line, you can do this executing the following command:

docker container run -it centos /bin/bash

To list all active containers, type:

docker container ls

You can view both active and inactive containers with the following line:

docker container ls -a

To remove docker containers, execute the following command:

docker container rm [container_id]

Those are some of the most useful commands for Docker. In this tutorial, we learned how to install Docker on Centos 7 and how to use the docker command line interface.