Common container startup failures in Docker - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the error 'OCI runtime create failed' usually indicate when starting a Docker container?

It means the container runtime failed to create the container. This often happens due to permission issues, missing files, or invalid configurations.

beginner

Why might a Docker container exit immediately after starting?

Because the main process inside the container finished or crashed. Containers stop when their main process ends.

beginner

What is a common cause of 'port already allocated' error in Docker?

Trying to start a container that wants to use a port already in use by another container or process on the host.

intermediate

How can missing environment variables cause container startup failures?

If the container expects certain environment variables to configure its app and they are missing, the app may fail to start.

beginner

What does a 'no such file or directory' error mean when starting a container?

It means the container tried to run a command or access a file that does not exist inside the container image or volume.

What happens if the main process inside a Docker container exits immediately?

A The container restarts automatically

B The container stops running

C The container runs in the background

D The container ignores the exit

Docker containers stop when their main process ends, so if it exits immediately, the container stops.

Which error indicates a port conflict when starting a Docker container?

A port already allocated

B no such file or directory

C permission denied

D container not found

The 'port already allocated' error means the port is in use by another container or process.

What is a common reason for 'permission denied' errors when starting containers?

A Port conflicts

B Missing environment variables

C Trying to access files or directories without proper rights

D Container image not found

Permission denied errors happen when the container or Docker daemon lacks rights to access needed files or directories.

If a container fails because it cannot find a command to run, what is likely the cause?

A The command is missing inside the container image

B The container has no network

C The container is out of memory

D The Docker daemon is down

A missing command inside the container image causes 'no such file or directory' errors at startup.

How can missing environment variables affect container startup?

A The container will restart repeatedly

B The container will ignore them and start normally

C The container will automatically set default values

D The app inside the container may fail to start

Many apps rely on environment variables for configuration; missing them can cause startup failure.

Explain three common reasons why a Docker container might fail to start.

Think about what the container needs to run properly.

Describe how environment variables can impact container startup and what happens if they are missing.

Consider the role of environment variables in app configuration.