1. Docker Daemon Is Not Running
Error:
Cannot connect to the Docker daemon at unix:///var/run/docker.sock
Simple fixes:
sudo systemctl start docker
sudo systemctl enable docker
sudo systemctl status docker
2. Container Exited Immediately
The container’s main process stopped, for example, the CMD script finished. Now run it in interactive mode to debug:
docker run -it /bin/bash
Now you can check the log with the following command:
sudo docker logs 021de3ad8869
Server running at http://localhost:3000
3. Check If the Port is Already in Use
Error starting userland proxy: listen tcp 0.0.0.0:3000: bind: address already in use
Check the busy port with the following command:
sudo lsof -i :3000
Stop or, if required then change the port in your Docker command or docker-compose.yml:
4. Image Build Fails
Failed to solve with the frontend Dockerfile.v0: failed to create LLB definition
Check your Dockerfile syntax (missing FROM, RUN, or incorrect COPY paths).
Clean up and rebuild:
docker builder prune -a
docker build -t myapp .
5. Volume Mount Permission Denied
Permission denied when accessing the mounted volume
Grant ownership to your current user or in docker-compose.yml, use user mapping shown below, respectively:
sudo chown -R $USER:$USER /path/to/volume
And in docker-compose.yml
services:
web:
image: nginx
volumes:
- ./html:/usr/share/nginx/html
user: "3000:3000"
6. Network Connection Issues
Could not resolve the host or network unreachable inside the container
For this, restart docker networking and recreate the default network:
sudo systemctl restart docker
docker network rm bridge
docker network create bridge
The majority of Docker errors are caused by the daemon not operating, improper file permissions, or network/port conflicts. You can maintain the health and functionality of your containers with a few basic commands and recommended practices.