See my Relax-and-Recover upstream issue https://github.com/rear/rear/issues/841

Currently the rear recovery system contains rear configuration files that are specific for the one single system where "rear mkbackup" was run.

"rear mkbackup" creates a bootable ISO image of a rear recovery system (i.e. what "rear mkrescue" does) plus a backup of the files (i.e. what "rear mkbackuponly" does).

Assume one has 100 servers with identical hardware of type A and 200 servers with identical hardware of type B, then (I hope) it is possible to have only one bootable ISO image for all type A servers and one for all type B servers.

This way one can use one same fixed rear recovery system for various sufficiently similar systems (i.e. systems where the same rear recovery system works but the only differences are in the rear configuration files).

This way one does no longer need to store 100 + 200 ISO images for each individual server but only two of them: one type A ISO image and one type B ISO image.

This should in particular mitigate the problem that UEFI bootable ISO images are much bigger than traditional BIOS bootable ISO images for example almost 450MiB for UEFI versus less than 120 MiB for BIOS, cf. https://github.com/rear/rear/issues/810#issuecomment-205783287

For recovery of a particular type A server one boots the type A ISO image on type A replacement hardware and in the type A rear recovery system a command like "rear recover HOSTNAME" first downloads rear configuration files for HOSTNAME and then proceeds as usual (i.e. it recreates the particular type A server system).

A consequence is that the recovery system network setup when booting a type A rear recovery system must work without HOSTNAME-specific rear configuration files (i.e. via automatic network setup like DHCP).