dockerfile - Explore Docker's image files if container exits immediately?

Question

I have a Docker image that I pulled from Docker hub.

When I run docker run image_name, container exits immediately.

I don't have access to the source code of the Docker image, including Dockerfile. All I have is an image I pulled from hub.docker.com.

I need to debug/see what is inside the image (e.g. see and explore image's filesystem), without running it as a container.

Is it possible?

Answer 1

Start a container from desired image like this:

docker run -it --rm image_name bash

-i Keeps STDIN open even if not attached

-t Allocates a pseudo-tty

--rm prunes stopped container after exit

bash executes the specific command in the container. You can execute any valid command.

Example docker run -it --rm centos:7 pwd outputs / (root directory).

Update: In some cases, where image's entrypoint uses bash/sh -c format above command(docker run -it --rm image_name bash) will not work because bash will be treated as additional argument to image's orignal entrypoint.

In such case you can use the --entrypoint flag for achieving the same result:

docker run -it --entrypoint "/bin/bash" image_name