I'd like to create a standard yum/rpm repository with package signing and whatever other best practices exist.
What is the procedure to add RPM, sign it and update the repo xmls?
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You would use the createrepo command to do this.
Make a folder containing the files you wish to distribute. Run createrepo.
From there, you can create a .repo file describing the location of the repository. This file would be distributed to the systems that require access to the repository. That's about it.