Docker is a great way to build multiple apps with different environments for various purposes, all in your local system without changing much of the settings of your local system. Since everything is run in Linux Containers, we do not need to worry about any changes happening to our Host OS.
There are multiple ways to install Docker in your Ubuntu system like Installing directly from Ubuntu Software centre, Downloading the Deb package and install it from the .deb file etc.
We will install by adding the Docker repositories in our System and then install it from those repository. This way we will get the latest stable Docker version for our system.
Below are the steps.
Install Docker on Ubuntu
Step 1: A pre-step of Updating before we start:
Let’s update the apt package index first:
sudo apt update
Step 2: Install required packages
Install packages to allow apt to use a repository over HTTPS:
sudo apt install \ apt-transport-https \ ca-certificates \ curl \ gnupg-agent \ software-properties-common
Step 3: Add Docker GPG Key
Add Docker’s official GPG (GNU Public Guard) key:
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
Step 3.1: Verify the Key
Verifying the key with the fingerprint 9DC8 5822 9FC7 DD38 854A E2D8 8D81 803C 0EBF CD88, by searching for the last 8 characters of the fingerprint.
sudo apt-key fingerprint 0EBFCD88
# Output pub rsa4096 2017-02-22 [SCEA] 9DC8 5822 9FC7 DD38 854A E2D8 8D81 803C 0EBF CD88 uid [ unknown] Docker Release (CE deb) <firstname.lastname@example.org> sub rsa4096 2017-02-22 [S]
Step 4: Select a Docker Channel and target CPU Arch to install
There are multiple repository channels like stable, nightly, test where you can install Docker from. You just need to give the name of the particular channel. We will install from the
stable repository. If you wish to see the nightly and test channels, you can check here.
Docker is available for Multiple CPU architectures like x86_64/amd64, armhf, arm64 etc.
Step 4.1: Determine CPU Architecture
Before starting the Install, let’s determine our CPU architecture
# Output amd64
My system has the
amd64 architecture, so we will install Docker for that architecture.
If you get some other value for your architecture like
s390x please replace the arch value in the below command accordingly. For eg. [arch=s390x].
Step 4.2: Add Channel and CPU Arch name
So, Let’s add the
amd64 arch in our docker repository name, since our CPU Arch is amd64 and stable channel for the stable release of Docker.
sudo add-apt-repository \ "deb [arch=amd64] https://download.docker.com/linux/ubuntu \ $(lsb_release -cs) \ stable"
Step 5: Update package index with new repositories added
Update the apt package index.
sudo apt update
Step 6: Install Docker CE on Ubuntu
We will now Install the latest version of Docker
sudo apt-get install docker-ce docker-ce-cli containerd.io
NOTE: If you wish To install a specific version of Docker CE, list the available versions in the repo, then select and install: 1. List the versions available in your repo: apt-cache madison docker-ce # Output
docker-ce | 5:18.09.0~3-0~ubuntu-xenial | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
docker-ce | 18.06.1~ce~3-0~ubuntu | https://download.docker.com/linux/ubuntu xenial/stable amd64 Packagesb. Install a specific version using the version string from the second column, for example, 5:18.09.0~3-0~ubuntu-xenial. sudo apt-get install docker-ce=VERSION_STRING docker-ce-cli=VERSION_STRING containerd.io
Step 7: Run and Verify Docker is installed in our Linux system
Now, Verify that Docker CE is installed correctly by running the hello-world image.
sudo docker run hello-world
This will download the
hello-world pre-compiled docker image, run it, print a message and exit.
So our docker installation is ready to go and you can start creating and downloading containers to run multiple apps as you wish.
The After Steps
If you are still with me here, you might want to go through a few more steps to work with more ease with your docker installation.
Step 8: Check docker group
So, Docker Community Edition (Docker CE) is installed. The installation also creates a
docker group in our system. Let’s check our
/etc/group file to confirm.
sudo less /etc/group
Last line of the above file shows:
Step 8.1: Add User to Docker group
Now, though the
docker group was added in our system, like we saw in the
/etc/group file, there were no users added to the
docker group yet.
You will have to add your user to the docker group in order to use the
docker commands without
sudo. Else, you will always need to use
sudo to allow non-privileged users to run
So let’s go ahead and add our user to
docker group so that we can use the
docker commands without needing to pre-pend
sudo usermod -aG docker <your_username>
Now, we will have to logout and login again into the system for the changes to take effect. Since, we’ve added our username to the docker group, we don’t need to use
sudo, after logging in.
Note: If you get Permission error, it's probably because your user does not have the necessary permissions to work with the
dockercommands yet. If you are testing on a Virtual Machine, you might have to restart the Virtual Machine.
So now, let’s run
docker without prepending
sudo and verify. We will run the hello-world image, again.
docker run hello-world
And it does the expected thing!
So our Docker installation is now good to go and we can now create our containers and start developing our apps inside them!