Using Rocky 9 with local RHEL 9 install repositories - how much trouble do I need to expect?

In an offline network (so no Internet connection!) we have some RHEL 9 servers and local RHEL 9 repository mirrors (baseos, appstream, etc) from which we can install and update.

Now I want to use an open-source Linux distribution accessing these RHEL 9 repositories for installs and updates.

I was thinking of using Rocky Linux 9 for this. Is Rocky 9 and RHEL 9 based on the same structure? Can I use our RHEL 9 repositories mirrors with a Rocky 9 OS?

Or how much trouble do I need to expect when I install software on Rocky 9 from RHEL 9 repository mirrors?

Thanks for any advice!

PS: I have tried CentOS Stream 9 with the RHEL repos and that seems to works OK, but I thought Rocky is more stable and maybe closer to RHEL than CentOS Stream which is suppose to be a development OS…

If you do install RHEL packages from RHEL repos, then your system becomes RHEL, doesn’t it?

If you can maintain local RHEL 9 repo mirrors, then you should be able to maintain Rocky 9 repo mirrors too (given enough disk space).

Expect your system to break if you are installing RHEL packages/updates on CentOS or Rocky. That is just a silly thing to even think of doing.

If you have CentOS systems - mirror the CentOS repositories locally like you are doing with RHEL. The same with Rocky, mirror those as well. If you don’t have the disk space, and only have disk space to mirror RHEL, then just stick with using RHEL systems. As soon as you apply RHEL updates to CentOS or Rocky, those systems are no longer CentOS or Rocky as @jlehtone said. At which point, you are on your own when things go wrong. Don’t expect assistance to fix it.

Thanks for chiming in, @jlehtone and @iwalker.

The problem is not only the disk space, but the mirrors are provided by the organisation and I cannot easily establish new mirrors.

Well, I cannot easily create a RHEL image for wsl -that’s where the new system will sit: on a Windows machine under wsl. For Rocky it’s easy however to get container images for wsl…

From looking at package names Rocky Linux repos don’t look too different from RHEL.

Package names will be the same because Rocky is based on RHEL. However that doesn’t mean you can update your system using RHEL packages. Because then you will be converting your Rocky install to RHEL.

Ask the people who manage the mirrors if they can mirror Rocky for you. If not, then you are stuck and will have to download Rocky packages directly from the internet.