Just be careful if you use Dovecot MDA, as it’s configuration files format changed. There’s a nice guide on dovecot’s documentation covering this change.

I remember it being none, i modified my app source to pount to the newer release codebame, then apt update && apt upgrade. I had everything as a container on my minipc and no extreem modifications to the base OS to make my upgrades (both software and hardware) as easier as possible.

I snapshot my machine, set it to go overnight, went to bed. Woke up, 24% done “Do you want to use the package maintainer’s version?”. Grr. Went smooth though.

How much pain you should expect is easily answered: Expect several things to break and having to do a full reinstall. So back up everything first.

It will probably not happen, but you should always expect the worst (out of the realistic at least…) outcome and be prepared.

I’ve yolo’d every major upgrade from debian 8 to 13 without any backups of configs and survived… (dont do that though)

For most desktop systems where you’re not dicking around with files in /etc, there is almost no pain ever

For servers, dealing with the “do you want to install the maintainers version of ____.conf”, sucks… trying to remember all the things i put in php.ini is a pain

Probably skill issue

Most of my infra is Debian, and I did it without serious incident:

#Update everything to latest
apt update && apt upgrade && apt full-upgrade && apt --purge autoremove
reboot

#Verify that debian_version is 12.x (STOP IF NOT 12!)
cat /etc/debian_version

#Check for any pinned or held packages
apt list '?narrow(?installed, ?not(?origin(Debian)))'
apt-mark showhold

#Swap bookworm for trixie in repo files
sed -i 's/bookworm/trixie/g' /etc/apt/sources.list
sed -i 's/bookworm/trixie/g' /etc/apt/sources.list.d/*

#Carry out update
apt update
apt upgrade --without-new-pkgs -y
apt full-upgrade -y
reboot

#Verify that debian_version is 13.x
cat /etc/debian_version

#Modernize apt sources to v3
apt modernize-sources -y

And then maybe apt update to make sure the updates still work OK.

Sometimes you have to make changes to certain repos that don’t have Trixie manifests, but that’s easy enough to roll back.

Make sure linux headers stay installed. Mine didn’t for some reason and then zfs dkms didn’t compile anymore. All I had to do was install it again, though, so the googling why it didn’t compile was the hard part. The boot disk was luckily just ext.

The first sentence gives away, that this is not a technical, but a psychological question. I think most of us know this feeling of this kind of urge, I’d say plan ahead, backup then upgrade. Or -depending on your usecase- a clean install and rebuild satisfies the urge even better. :) (no offense, I did this myself multiple times)

I backed up my configs, made snapshots, and rebuilt each VM from scratch. If I forgot to copy a cron script, i pulled it from the snapshot. It took a full Saturday, but it was a chance to apply everything ive learned the last 3 years and improve some architecture decisions I’d made when i was first learning. With proxmox, you can build a VM that has the basic things you’ll change on every machine (networking, docker, automatic updates, ssh keys, monitoring) and clone it for each server you need.

I updated NAS, VPS and Raspberry Pis not so long ago. All when smooth and without issue.

Annecdata here, but I didn’t have any significant problems on like 5 servers. I recall there being one minor edge case, but I don’t remember what it was (sorry). But other than that it was really easy. Even my nvidia drivers continued to work (for cuda, not GUI), which was really surprising. ZFS, docker, ssh, nfs, etc. all continued to work without any problems.

If you want to do a test run, create a 12 VM and install your same package list, then upgrade it and see what happens. That could take as little as an hour to do, but more likely a few hours if you want to really take time to inspect everything after the upgrade.

The upgrade itself is never a problem.

The real problem is when your server is running an old software that breaks after the update.

For example I had an old php/drupal site and it broke after upgrading debian because the upgrade also updated php to a newer version that is not supported by that old version of drupal.

I recently upgraded my gaming pc from Bookworm to Trixie. It was fairly painless. Had to fiddle with some third party repos, but I anticipated that and read up on them beforehand.

Do you run all your services in docker? If yes, the upgrade should be nothing more than the upgrade including switching the docker repo to the new version codename and rebooting

This is why I’ve started running most services as containers inside of an LXC container in Proxmox