I want to ask how SHOULD I do mentioned migration.
- backup settings (system tool),
- install needed modules (kernel, software, LuCI) on target,
- restore config on target (while changing "source" IP).
- (implied) config files with changed syntax will be converted on the fly as I get to related config page (LuCI)?
Is this correct or I am missing something?
I use this for:
- bridge (AP WiFi <-> Lan),
- AP (second WiFi, RT5370 card, routing),
- radio (wget + madplay).
there is too big gap between 18.06 and 21.02, and you change hardware too so my recommendation:
- do backup of old with list of installed packages
- fire up the new router, install openwrt from scratch
- configure the new router from the beginning by hand, do NOT restore the old backup as there are many changes happened since 18.06. use the backup as reminder, collection of hints what and why you did but configure it from scratch.
can use the content of the backup as reference for the settings, on the new device.
you can run them in parallell, by daisy chaining, compare the settings in two browser windows/tabs.
No, config backup tarballs are not compatible between different devices (v1 and v3 are pretty different), not even between different devices of the same model/ revision (as they often contain MAC addresses and similar, which would break havoc on your network if replicated).
No, restoring a backup circumvents all migration support and safeguards, it is just extracted to the target system as-is, clobbering anything which might already be there. Restoring an old backup tarball on a newer release is a sure way to (soft-)brick your device, don't do that,
OK, so what do You (all) suggest?
- install 18.06 on V3, then "sysupgrade"?
- any other way?
I want to keep settings (DHCP leases, WiFi / IP config, bridges config, etc). As there is much configuration non default.
Use your old tarball for visual-reference-only, leave your old router as-is, set up the new one from scratch, step by step.