Installing Docker on Linux

Prerequisites

Before installing Docker on Linux, ensure your system meets these requirements:

Linux Requirements

• 64-bit OS: Most modern distributions supported
• Kernel: Version 3.10 or higher
• RAM: Minimum 2GB (4GB recommended)
• Storage: 10GB minimum for Docker images and containers

Installing Docker on Ubuntu/Debian

Step 1: Update Package Index

sudo apt-get update

Step 2: Install Prerequisites

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

Step 3: Add Docker's Official 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 4: Set Up Repository

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

Step 5: Install Docker Engine

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

Step 6: Verify Installation

sudo docker run hello-world

Installing Docker on CentOS/RHEL

Step 1: Install Required Packages (CentOS)

sudo yum install -y yum-utils

Step 2: Add Docker Repository (CentOS)

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

Step 3: Install Docker (CentOS)

sudo yum install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin

Step 4: Start Docker (CentOS)

sudo systemctl start docker
sudo systemctl enable docker

Step 5: Verify Installation (CentOS)

sudo docker run hello-world

Installing Docker on Fedora

Step 1: Install Prerequisites (Fedora)

sudo dnf -y install dnf-plugins-core

Step 2: Add Docker Repository (Fedora)

sudo dnf config-manager --add-repo https://download.docker.com/linux/fedora/docker-ce.repo

Step 3: Install Docker (Fedora)

sudo dnf install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin

Step 4: Start Docker (Fedora)

sudo systemctl start docker
sudo systemctl enable docker

Step 5: Verify Installation (Fedora)

sudo docker run hello-world

Post-Installation Steps

Running Docker Without sudo

By default, Docker requires root privileges. To run Docker as a non-root user:

Step 1: Create Docker Group

sudo groupadd docker

Step 2: Add Your User to Docker Group

sudo usermod -aG docker $USER

Step 3: Log Out and Back In

For the changes to take effect, log out and log back in. Or run:

newgrp docker

Step 4: Verify

docker run hello-world

You should now be able to run Docker commands without sudo.

Configure Docker to Start on Boot

Ubuntu/Debian/Fedora (systemd)

sudo systemctl enable docker.service
sudo systemctl enable containerd.service

CentOS/RHEL 7 and earlier

sudo chkconfig docker on

Configure Docker Daemon

Create or edit /etc/docker/daemon.json:

{
  "log-driver": "json-file",
  "log-opts": {
    "max-size": "10m",
    "max-file": "3"
  },
  "storage-driver": "overlay2"
}

Restart Docker after making changes:

sudo systemctl restart docker

Troubleshooting Linux Installation

Docker Service Not Starting

Problem: "Failed to start docker.service"

Solution:

# Check service status
sudo systemctl status docker

# View logs
sudo journalctl -u docker

# Restart service
sudo systemctl restart docker

Permission Denied Error

Problem: "Got permission denied while trying to connect to the Docker daemon socket"

Solution:

1. Add user to docker group: sudo usermod -aG docker $USER
2. Log out and back in
3. Or use: newgrp docker

Firewall Issues

Problem: Cannot pull images due to firewall

Solution:

# For firewalld
sudo firewall-cmd --permanent --zone=trusted --add-interface=docker0
sudo firewall-cmd --reload

# For UFW
sudo ufw allow 2375/tcp
sudo ufw allow 2376/tcp

Storage Driver Issues

Problem: "Error starting daemon: error initializing graphdriver"

Solution:

1. Check available storage drivers: docker info
2. Set appropriate driver in /etc/docker/daemon.json
3. Common drivers: overlay2 (recommended), aufs, devicemapper

Testing Your Installation

Let's verify everything works correctly:

1. Check Docker Version

docker --version
docker compose version

2. View System Information

docker info

This displays:

• Number of containers (running, paused, stopped)
• Number of images
• Storage driver information
• System resources

3. Run a Test Container

docker run -d -p 8080:80 nginx

Then visit http://localhost:8080 in your browser or use curl:

curl http://localhost:8080

You should see the Nginx welcome page!

4. List Running Containers

docker ps

5. Stop and Remove the Container

docker stop $(docker ps -q)
docker rm $(docker ps -aq)

Linux-Specific Configuration

SELinux Considerations (CentOS/RHEL/Fedora)

If using SELinux:

# Check SELinux status
getenforce

# Set SELinux to permissive mode for testing
sudo setenforce 0

# Make it permanent (edit /etc/selinux/config)
SELINUX=permissive

For production, configure proper SELinux policies instead of disabling it.

AppArmor Considerations (Ubuntu/Debian)

Docker works with AppArmor by default. If you encounter issues:

# Check AppArmor status
sudo aa-status

# Reload AppArmor profiles
sudo systemctl reload apparmor

Resource Limits

Configure resource limits in /etc/docker/daemon.json:

{
  "default-ulimits": {
    "nofile": {
      "Name": "nofile",
      "Hard": 64000,
      "Soft": 64000
    }
  }
}

Docker Compose on Linux

Docker Compose is now included as a plugin. Verify:

docker compose version

If you need standalone Docker Compose:

sudo curl -L "https://github.com/docker/compose/releases/latest/download/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose
sudo chmod +x /usr/local/bin/docker-compose

Best Practices for Linux

1. Keep Docker Updated

# Ubuntu/Debian
sudo apt-get update && sudo apt-get upgrade docker-ce docker-ce-cli

# CentOS/RHEL
sudo yum update docker-ce docker-ce-cli

# Fedora
sudo dnf upgrade docker-ce docker-ce-cli

2. Monitor Resource Usage

# View container resource usage
docker stats

# View disk usage
docker system df

3. Clean Up Regularly

# Remove unused images
docker image prune

# Remove all unused resources
docker system prune -a

4. Configure Logging

Prevent logs from filling disk:

{
  "log-driver": "json-file",
  "log-opts": {
    "max-size": "10m",
    "max-file": "3"
  }
}

5. Use systemd for Management

# Start Docker
sudo systemctl start docker

# Stop Docker
sudo systemctl stop docker

# Restart Docker
sudo systemctl restart docker

# View Docker status
sudo systemctl status docker

Uninstalling Docker

If you need to remove Docker:

Ubuntu/Debian

sudo apt-get purge docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin
sudo rm -rf /var/lib/docker
sudo rm -rf /var/lib/containerd

CentOS/RHEL/Fedora

sudo yum remove docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin
sudo rm -rf /var/lib/docker
sudo rm -rf /var/lib/containerd

What's Next?

Now that Docker is installed on Linux, you can:

• Learn about Docker images and containers
• Build your first Docker application
• Explore Docker Compose for multi-container apps
• Set up production Docker deployments
• Configure Docker Swarm for orchestration

Your Docker journey on Linux has begun!