Adding centOS tag

[arthurdm]

Adding a tag for CentOS-based image. This image runs as non-root, which allows it to run in restricted environments such as OpenShift.

This image is also important for developers that want to use CentOS for dev and RHEL for production.

[tianon]

This Dockerfile includes COPY --from=websphere-liberty:kernel ... which suffers from the same issues as multi-stage builds (enumerated/discussed over in #3383 (comment)).

[arthurdm]

Thx @tianon - I added a comment in that issue.

[tianon]

I'm not sure I fully understand the importance of providing a CentOS-based image as well -- isn't part of the point of using Java and tools like WebSphere Liberty that you don't care as much about the underlying operating system? What does this change for usage of the image from a functional perspective?

[arthurdm]

Yes, you're correct that for Java and Liberty it doesn't matter as much which OS is under (as long as it's one of the supported OS).

There were two issues though:

1. There wasn't any pattern for customers to follow to build a Dockerfile that contained IBM's JRE + Liberty + an OS that wasn't Ubuntu or Alpine. So we have seen customers build many incorrect Dockerfiles trying to get OS such as CentOS and RHEL to work - many times using OpenJDK instead of IBM's JRE because it was easier to get that. There's a lot of performance benefits for using the combo (JRE + Liberty), so we wanted to ensure we have a Dockerfile (and image) that had that.

2. Customers that deploy into OpenShift need an image that runs as non-root. Our new CentOS based image (which is popular OS for such platform) accomplishes that.

[arthurdm]

hi @tianon - any updates on this?

[yosifkit]

This comment still applies: #4326 (comment). Unfortunately, none of our tooling can handle multi-stage builds including just COPY --from another official image.

[arthurdm]

ok. thanks @yosifkit - I will close this PR then.