Config Files to backup before OS Reinstall?

My LEAP 15 system has crapped out for some unknown reason, the MDADM Raid isn’t bootable anymore. I noticed some strange issues almost immediately after upgrading from 42.3 about 10 days ago that I have been slowly weeding through, but after a zypper update and a reboot, now it won’t boot. All the drives are intact and everything else looks fine. From the rescue prompt, I’ve done a Grub reinstall, still no love. I’ll probably try the upgrade option from the USB install to see if that will at least limp it to life, but it’s been years since I’ve done a fresh install on this system so I’m leaning towards formatting the system partitions and doing a fresh install.

I’m running an MDADM RAID, with /boot, /, /home, and /data as the different ext4 partitions. The first three partitions are on two mirrored drives, and /data is a RAID 5 among 4 drives. I’ll format the /boot and / partitions and do a reinstall. Therefore I shouldn’t loose anything in the home directories or on the data drive.

Big question is, as it’s been a VERY long time since I’ve done a reinstall like this, what critical files should I take note of before reformatting the drives? I’ve already grabbed the crontabs and the fstab. What else should I consider given this is a software RAID, or is it pretty easy to manage via the installer?

Thanks!

Roughly: /etc and /var
Do not simply copy those folders back, but only use them as a reference

On the RAID config I can not give much comment, except that IMHO it is best setup fresh.

Make a backup of the whole of /etc. Then you should have all the system config files.

But you should not blindly copy the old files over the new ones. They are for reference if you doubt how it was configured earlier when you configure new. I often call it “merge intelligent”.

I think your fstab example is a good example. During the new installation you have plenty chance in the partitioning and mounting section to set that as needed, but it is always nice that you can see in your old fstab: Oh yes, /data was ext4 and it was on device …

Perfect, thanks for the quick replies! I’ll grab both /etc and /var and use for reference only (esp when it comes to re-installing some of the programs, I know I’ll need to go back to see how things were configured).

Another related question that popped in my mind: When I reformat the / and /boot partitions, should I do them as btrfs? When I built this system originally, btrfs wasn’t developed yet. Or would there be really no advantage unless I convert /home as well?

No Btrfs for /boot.

You could use Btrfs for / (it is the default for /), but you should have space enough (the advice is 40 GB for Btrfs instead of 20GB for ext4, you could go for less Btrfs if you switch snapshotting off). Thus if you have 20 GB at the moment, I assume using ext4 again is most easy.

My most recent RAID “installation” was less than a month ago. I installed /boot, /, swap and /usr/local to partitions on a new SSD. When done, I plugged in the old MD RAID1 disk pair on which 13.1, 13.2, 42.1, 42.3 and TW had been included, and used the “old” 42.3 mdadm.conf as-is for mounting the still-relevant md devices to /home and data.