Introduction
Docker is a popular software package that creates and manages containers for application development.
Docker creates a uniform interface so that almost any application running on it is compatible with most operating systems. Developing in Docker also speeds up applications, since it shares the kernel and other Linux resources.
This will be a guide on How To install Docker on CentOS 7.
Prerequisites
- A maintained/supported version of CentOS (Docker doesn’t test or support outdated versions)
- A user account with sudo privileges
- Terminal access (Right-click desktop, click Open in Terminal)
- CentOS Extras repository – this is enabled by default, but if yours has been disabled you’ll need to re-enable it
- Software package installer yum
Installing Docker on CentOS 7 with yum
Installing from Docker repositories using the yum command is the easiest and most popular method.
Step 1: Update Docker Package Database
In a terminal window, type: sudo yum check-update
Allow the operation to complete.
Step 2: Install the dependencies
In a terminal window, enter the command:
sudo yum install -y yum-utils device-mapper-persistent-data lvm2
The –y switch indicates to the yum installer to answer “yes” to any prompts that may come up. The yum-utils switch adds the yum-config-manager. Docker uses a device mapper storage driver, and the device-mapper-persistent-data and lvm2 packages are required for it to run correctly.
Step 3: Add the Docker repository
In the terminal window, input the command:
sudo yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
This command will add the Docker CE stable repository. You’ll need this repository, even if you want to install the edge or test versions of Docker.
A stable release is tested more thoroughly and has a slower update cycle. Edge release updates are more frequent but are not subjected to as many stability tests.
NOTE: If you’re only going to use the stable release, don’t enable these extra repositories. The Docker installation process will default to the latest version of Docker unless you specify otherwise. Leaving only the stable repository enabled makes sure that you aren’t accidentally updating from a stable release to an edge release.
Step 4: Install Docker On CentOS using yum
In a terminal window, enter the command:
sudo yum install docker
The system should begin the installation.
It is possible that your operating system will ask you to accept the GPG key, which is like a digital fingerprint, so you know whether to trust the installation.
The fingerprint should match the following format:
060A 61C5 1B55 8A7F 742B 77AA C52F EB6B 621E 9F35
Step: 5 Manage Docker Service
You have installed Docker, but the service is not running.
You can start the service, enable it to run at startup, or check the status of the service by running the following commands (respectively):
To start Docker: sudo systemctl start docker
To enable Docker: sudo systemctl enable docker
To check the status of Docker on CentOS: sudo systemctl status docker
Install a Specific Version of Docker on CentOS
If you know that there is a specific release that you need, or you want to choose which version you want to install, start by listing the available versions.
Type the following in your terminal window:
yum list docker-ce --showduplicates | sort –r
The system should give you a list of different versions from the repositories you have enabled above.
Install the selected version with the command:
sudo yum install docker-ce-<VERSION STRING>
The <VERSION STRING> is found in the middle column and is the first part of the alphanumeric code before the hyphen.
Conclusion
Docker installation on CentOS 7 is a bit easier than installing on Ubuntu.
Many of the repositories and dependencies are already configured by default. Once you’ve got it installed, you should be ready to start playing with Docker containers – happy coding!