Some questions about Docker Hub

Question

I am fairly new to using Docker and I went to Docker Hub to select a base image, but I have some questions. In particular, I want to use a non-alpine amazoncorretto:latest, and am wondering:

• If I use "amazoncorretto:latest" in a Dockerfile, eg:

  FROM amazoncorretto:latest

is there a way to find out what specific version actually is used at runtime? For example can I use "exec" on the running container and find out exactly which image/version is being used? I am asking because where I work, we have to get the specific version pre-approved.

• I noticed that in Docker hub (eg: https://hub.docker.com/_/amazoncorretto?tab=tags ) for each tag, eg, the "amazoncorretto:latest", it shows 2 images, one without a "v8" and the other with a "v8". What does that "v8" mean?

• Also, some tags have "al2" in the tag. What does that "al2" mean?

Thanks, and sorry for all the really newbie questions, and thanks in advance!

Jim

Answer 1

This isn't really a Docker question: how would you normally tell what version of Correto you're using? It looks as if java -version provides this information, so you can just run that command in a container:

$ docker run --rm docker.io/amazoncorretto:latest java -version
openjdk version "1.8.0_332"
OpenJDK Runtime Environment Corretto-8.332.08.1 (build 1.8.0_332-b08)
OpenJDK 64-Bit Server VM Corretto-8.332.08.1 (build 25.332-b08, mixed mode)

---

It is possible to figure out some of this from the available Docker tags. If you look at the information for the latest tag, it shows, it shows that the linux/amd64 version of the image has digest 1395e022da6d . If we look at the list of available tags, we see the same digest for the tag 8u332 .

It's fairly common -- but by no means universal! -- for the latest tag to be an alternative name for a version-specific tag.