Troubleshooting "unable to start" Error

Full error message:

CircleCI was unable to start the container because the container entrypoint or command failed to start.

This typically means that the passed entrypoint or command is not found or is not valid.  Try clearing the entrypoint/command values.
Original error: Error response from daemon: oci runtime error: container_linux.go:247: starting container process caused "process_linux.go:245: running exec setns process for init caused \"exit status 15\""

Cause

The error states the container you are using does not have a valid entrypoint command in response to one attempting to be ran. `Try clearing the entrypoint/command values`

Resolution

1. If you see the line `command: /sbin/init` or similar in your config.yml file, you may try removing it if you recently changed your Docker image.

2. If using a custom Docker image, double check your entrypoint or command values in your dockerfile. You will also need to add a special LABEL to your dockerfile for CircleCI. https://circleci.com/docs/2.0/custom-images/#adding-an-entrypoint