Installing Docker on a DigitalOcean Droplet running Ubuntu is a standard procedure.¹ While DigitalOcean offers a “One-Click” Docker image in their marketplace, knowing how to install it manually ensures you have control over the version and configuration.

Here is the step-by-step guide to installing Docker Engine (Community Edition).

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Step 1: Update and Install Prerequisites

First, connect to your droplet via SSH.² Before installing, ensure your existing package list is up-to-date and install a few packages that allow apt to use packages over HTTPS.³

sudo apt update
sudo apt install apt-transport-https ca-certificates curl software-properties-common

Step 2: Add Docker’s Official GPG Key

You need to add the GPG key to ensure the software you’re downloading is authentic.⁴

curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg

Step 3: Add the Docker Repository

Add the Docker repository to your APT sources.⁵ This command dynamically inserts the correct repository for your specific version of Ubuntu.

echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

Step 4: Install Docker Engine

Now that the repository is added, update your package index again and install Docker.⁶

sudo apt update
sudo apt install docker-ce docker-ce-cli containerd.io

Step 5: Execute Docker Without Sudo (Optional but Recommended)

By default, the docker command must be run with sudo (root privileges).⁷ To run docker commands as your current non-root user (e.g., sammy or a standard user), add your user to the docker group:⁸

sudo usermod -aG docker $USER

Note: You must log out of the droplet and log back in for this group membership to take effect.

Step 6: Verify Installation

Once you have logged back in, verify that Docker is running and installed correctly:

1. Check Status:

   Bash

   sudo systemctl status docker
   

   You should see a green “active (running)” status.

2. Run a Test Container:

   Bash

   docker run hello-world
   

   If successful, Docker will download a test image and print “Hello from Docker!” along with some explanatory text.

Alternative: DigitalOcean 1-Click App

If you are creating a new droplet rather than using an existing one, you can skip the steps above by selecting the Docker image from the “Marketplace” tab during the Droplet creation process. This comes with Docker and Docker Compose pre-installed.

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