I don't really find the responses here at all helpful. They boil down to:
1. System backup files are restored manually.
2. We don't recommend you actually do it (we don't provide a rationale or an alternative).
3. See this link, which provides only the guidance already given in 1.
I am forced to go through a system backup / restore cycle because my hosting provider must upgrade the OS on my VM due to an upcoming end-of-life on support.
I take backups religiously, but nobody at the hosting provider can tell me whether simply restoring one on the new version OS will give me turnkey restoration, or whether I will have to do additional things by hand (and if so, what).
I have found plenty of CPanel/WHM documentation that says, "cPanel & WHM does not include an interface to restore system backup files. To restore content from system backup files, you must perform the restoration manually," but none that provides any reference to HOW to perform it manually. Since the command to make the backups is "/usr/local/cpanel/bin/backup" (a cpanel command) I am thinking that the restoration command would also be specific to cpanel, yet I can't find any documentation for one. In that directory, I see backup_restore_manager and restorepkg, but they both seem to be for account level restoration.
I am used to systems where you can upgrade OS levels without entirely wiping the system back to day zero, and it's terrifying to be forced stumbling into this morass, where I don't know what isn't going to work until it's too late to fix it.
How do I achieve what I need to achieve here?