Understanding the Error
docker: Error response from daemon: port is already allocated
Fix 1: Find What's Using the Port
# Check all Docker containers using port
docker ps --filter "publish=80"
docker ps -a | grep 80
# Check host processes
sudo lsof -i :80
sudo netstat -tlnp | grep :80
Fix 2: Stop Conflicting Container
# Stop specific container
docker stop container_name
# Remove it
docker rm container_name
Fix 3: Stop All Containers Using Port
# Find PIDs using port 80
sudo fuser -k 80/tcp
Fix 4: Use Different Host Port
# Instead of -p 80:80, use:
docker run -p 8080:80 nginx
# Now access on port 8080
Fix 5: Check for Stopped Containers
# Stopped containers still reserve ports
docker ps -a
# Remove all stopped containers
docker container prune
# Remove specific
docker rm container_id
Fix 6: Docker Network Conflict
# Check networks
docker network ls
# Remove unused networks
docker network prune
Fix 7: Reset Docker
sudo systemctl restart docker
