Installing Docker on Ubuntu 18.04 and Fixing Common Errors

Docker is a powerful platform for building, shipping, and running applications inside containers. Below is a step-by-step guide for installing Docker on Ubuntu 18.04, along with troubleshooting tips for resolving dependency errors you may encounter.

Step 1: Update Packages and Install Prerequisites

First, update your system and install required dependencies:

sudo apt-get update
sudo apt-get install \
    ca-certificates \
    curl \
    gnupg \
    lsb-release

Step 2: Add Docker’s Official GPG Key

Create a keyring directory and add Docker’s GPG key:

sudo mkdir -p /etc/apt/keyrings
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg

Step 3: Set Up the Docker Repository

Add the Docker repository to your sources list:

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

Then update your package index:

sudo apt-get update

Step 4: Install Docker

Now install Docker and related components:

sudo apt-get install docker-ce docker-ce-cli containerd.io docker-compose-plugin

Common Installation Error: Unmet Dependencies

During installation, you may encounter an error similar to this:

The following packages have unmet dependencies:
 gsettings-desktop-schemas : Breaks: mutter (< 3.31.4) but 3.28.4+git20200505-0ubuntu18.04.2 is to be installed
E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.

This typically indicates missing or conflicting packages.

Step 5: Fixing the Error

To resolve this issue, install the missing dependencies:

sudo apt install gsettings-desktop-schemas
sudo apt install build-essential

Then retry installing Docker:

sudo apt-get install docker-ce docker-ce-cli containerd.io docker-compose-plugin

Step 6: Verify Docker Installation

Run the hello-world test container to confirm everything is working:

sudo docker run hello-world

If successful, you should see output similar to:

Hello from Docker!
This message shows that your installation appears to be working correctly.

This confirms that the Docker client and daemon are communicating properly.