Add Docker installation script for Ubuntu (#3)

This script installs Docker on Ubuntu, ensuring prerequisites are met and the user is added to the Docker group.

Author: rezzcode

DevOps-Tools/docker/docker_install.sh

@@ -0,0 +1,76 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+echo "=== Docker installation script ==="
+
+# Ensure script is not run as root (recommended)
+if [[ "$EUID" -eq 0 ]]; then
+  echo "===XXX===> Do not run this script as root. Run as a normal user."
+  exit 1
+fi
+
+# Remove old Docker versions if present (ignore errors)
+echo "===> Removing old Docker packages (if any)..."
+sudo apt-get remove -y docker docker-engine docker.io containerd runc || true
+
+# Update package index
+echo "===> Updating package index..."
+sudo apt-get update -y
+
+# Install prerequisites
+echo "===> Installing prerequisites..."
+sudo apt-get install -y \
+  ca-certificates \
+  curl \
+  gnupg \
+  lsb-release
+
+# Add Docker's official GPG key
+echo "===> Adding Docker GPG key..."
+sudo install -m 0755 -d /etc/apt/keyrings
+if [[ ! -f /etc/apt/keyrings/docker.gpg ]]; then
+  curl -fsSL https://download.docker.com/linux/ubuntu/gpg \
+    | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg
+  sudo chmod a+r /etc/apt/keyrings/docker.gpg
+fi
+
+# Add Docker repository
+echo "===> Adding Docker APT repository..."
+echo \
+  "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.gpg] \
+  https://download.docker.com/linux/ubuntu \
+  $(. /etc/os-release && echo "$VERSION_CODENAME") stable" \
+  | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
+
+# Update package index again
+sudo apt-get update -y
+
+# Install Docker Engine
+echo "===> Installing Docker Engine..."
+sudo apt-get install -y \
+  docker-ce \
+  docker-ce-cli \
+  containerd.io \
+  docker-buildx-plugin \
+  docker-compose-plugin
+
+# Enable and start Docker
+echo "===> Enabling Docker service..."
+sudo systemctl enable docker
+sudo systemctl start docker
+
+# Add user to docker group (do not fail script if already added)
+echo "===> Adding user '$USER' to docker group..."
+sudo usermod -aG docker "$USER" || true
+
+sudo chown $USER /var/run/docker.sock
+
+# Verify installation
+echo "===> Verifying Docker installation..."
+docker --version
+docker compose version
+
+echo
+echo " ===> Docker installed successfully."
+echo " !!! ===> Log out and log back in for docker group changes to take effect."