the replacement inherited the configuration and not the habits

When new machines are built to replace an old one, the old one becomes the reference, and the comparison that matters is not between files. A parity audit set the retiring member against the freshly built replacements, and the configuration came out nearly identical: firewall, remote access, mounts, time synchronisation, the services themselves.

What differed was everything that runs without being asked. The new machines had no certificate renewal job at all, so they held valid certificates and nothing that would ever replace them, which is a scheduled outage with a date on it, invisible until the date. Memory ceilings on the backup legs were still at their old, too-low values. A network address translation rule that existed only on the old machine had never been carried across. And one backup job was still pinned to the machine it was supposed to leave, so it had been archiving the right thing in the wrong place.

The audit's useful output was a ranked list, not a green tick. A green tick would have been a claim about files. The list was a claim about behaviour, and every item had to be argued, because some differences were deliberate: the new machines did not need everything the old one had accumulated across its life, and saying which was which meant remembering why the new ones were built at all.

What it proves is that parity between machines is a behavioural property. The checklist that finds the missing jobs, ceilings and rules is worth far more than the one that confirms the files match, because the files were never what kept the fleet alive.