The 10 most common Docker errors with solutions

Various errors often occur when running or starting Docker containers. These errors can be caused by incorrect configurations, missing dependencies, network problems or faulty Docker images. Here are the most common errors and possible solutions:

1. image not found

• Description: The specified image name or tag is incorrect or does not exist in the Docker registry.
• Error message: Error response from daemon: pull access denied for <image>, repository does not exist or may require 'docker login'
• Solution: Make sure that the image name is correct, including the correct tag (e.g. nginx:latest). If it is a private image, log in with docker login.

2. port already in use

• Description: The specified host port is already occupied by another process or container.
• Error message: Error response from daemon: driver failed programming external connectivity on endpoint <container_name>: Bind for 0.0.0.0:<port> failed: port is already allocated
• Solution: Check which process is using the port by executing the command sudo lsof -i :<port> and change either the port of the running process or that of the new container.

3rd Container Exited Immediately After Starting

• Description: The container starts, but the main process ends immediately.
• Error message: Exited (0) or Exited (1)
• Solution: Check the Docker container log with docker logs <container_name> to see what went wrong. Possibly an environment variable or dependency is missing. Make sure that the CMD or ENTRYPOINT command defined in the Dockerfile is correct.

4. permission denied error

• Description: The container or the host system does not have the necessary authorizations for an action.
• Error message: permission denied, EACCES: permission denied, mkdir
• Solution: Make sure that the file system permissions are set correctly. Use sudo chown or chmod to configure permissions. Set --privileged or --user flags in Docker only as a last resort.

5 Cannot Connect to Docker Daemon

• Description: Docker client cannot connect to the Docker daemon.
• Error message: Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?
• Solution: Make sure that Docker is installed and the Docker daemon is started. Use sudo systemctl start docker or sudo service docker start. Check the permissions for the Docker socket.

6. network connectivity issues

• Description: Containers cannot connect to external networks or the host.
• Error message: Could not resolve host, network not found
• Solution: Make sure that the network is defined correctly. Check the network configuration in docker-compose.yml or use docker network ls to ensure that the required network is available.

7. volume mounting errors

• Description: Error when provisioning volumes because paths are incorrect or do not exist.
• Error message: Error response from daemon: invalid mount config for type "bind": bind source path does not exist
• Solution: Check whether the host path exists and is formatted correctly. Pay attention to the absolute path and that it begins with /.

8. out of memory (OOM)

• Description: The container or host runs out of memory due to resource restrictions or memory-intensive applications.
• Error message: Killed or OOMKilled
• Solution: Allocate more memory or limit the memory consumption of the container with --memory flag(e.g. --memory="1g"). Check the host memory with free -m.

9th Docker Daemon Configuration Issues

• Description: Incorrect configuration of the Docker daemon can prevent containers from being executed.
• Error message: Various, depending on the configuration error.
• Solution: Check and edit the configuration file /etc/docker/daemon.json. Use docker info and docker logs for further diagnostics. Restart the daemon with sudo systemctl restart docker.

10 Conflict Error

• Description: Conflict due to an existing container or image with the same name or tag.
• Error message: Conflict: The container name "/<container_name>" is already in use by container "<container_id>"
• Solution: Remove the existing container or rename the new container. Use docker rm <container_name> or docker rename.

These common Docker errors can be identified and corrected by carefully checking the logs, configuration files and running processes on the host system. Faulty volumes, images or network configurations can be solved by more precise definitions and corrections in the docker-compose.yml or Docker commands.