Is it possible to get bash access in NOT running container? - bash

Question

I able to run Flask API container successfully. But during the app execution it fails and stops the container for some reason.
I do checked container logs and noticed some file missing error is coming. Now I want to debug what file is missing by accessing /bin/bash of stopped container. But it throws an error saying container is not running.
docker exec -it CONTAINER /bin/bash
Is there any workaround to access bash in the STOPPED container?

Answer 1

No, you cannot.
However, it might be useful to either check the logs or specify bash as an entry point when doing a docker run
Checking logs: https://docs.docker.com/config/containers/logging/
docker logs <CONTAINER_NAME>
Shell Entry point: https://docs.docker.com/engine/reference/run/#entrypoint-default-command-to-execute-at-runtime
docker run --name <CONTAINER_NAME> --entrypoint /bin/bash <IMAGE_NAME>
If you container does not have /bin/bash, try
docker run --name <CONTAINER_NAME> --entrypoint /bin/sh <IMAGE_NAME>

Answer 2

You can try to use the docker commit command.
From the docs:
It can be useful to commit a container’s file changes or settings into
a new image. This allows you to debug a container by running an
interactive shell, or to export a working dataset to another server.
Resource with a example:
We can transform a container into a Docker image using the commit
command. All we need to know is the name or the identifier of the
stopped container. (You can get a list of all stopped containers with
docker ps -a).
docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS NAMES
0dfd54557799 ubuntu "/bin/bash" 25 seconds ago Exited (1) 4 seconds ago peaceful_feynman
Having the identifier 0dfd54557799 of the stopped container, we can
create a new Docker image. The resulting image will have the same
state as the previously stopped container. At this point, we use
docker run and overwrite the original entrypoint to get a way into the
container.
# Commit the stopped image
docker commit 0dfd54557799 debug/ubuntu
# now we have a new image
docker images list
REPOSITORY TAG IMAGE ID CREATED SIZE
debug/ubuntu <none> cc9db32dcc2d 2 seconds ago 64.3MB
# create a new container from the "broken" image
docker run -it --rm --entrypoint sh debug/ubuntu
# inside of the container we can inspect - for example, the file system
$ ls /app
App.dll
App.pdb
App.deps.json
# CTRL+D to exit the container
# delete the container and the image
docker image rm debug/ubuntu

Answer 3

You can't because this container is dead as well as turned down virtual machine is dead. You can check logs using docker logs command.
docker container ls -aq
docker logs <name_of_your_dead_container>

Answer 4

From the man pages from docker-run:
--entrypoint=""
Overwrite the default ENTRYPOINT of the image
So use something like:
docker run --entrypoint=/usr/bin/sleep 1000 ......
This will start the container and wait 1000 seconds, allowing you to connect and debug.