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.

I upgraded 50 boxes from 9 to 13 last week.

The two dovecot were the most work. Some guacd had trouble with file permissions and I had to manually install and enable a few php8.4 packages and manually apply powerdns db migration scripts.

Oh, powerdns renamed master/slave to primary/secondary, too.

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.

0.076

Update when you can afford downtime. The update should be painless but you know how it is: things go crazy when they shouldn’t. Every time.

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.

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’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

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.

On a normal setup without leads or crazy customisation, it’ll be a breeze 👍

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

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.

Is it painful? I’ve upgraded several versions without difficulty. “third party” repositories are problematic so be sure you follow the guidelines about disabling them.

Backup your data: the stuff you can’t just reconstruct.

The go for it. Worst comes to worst: reconstruct the system and applications and reimport the data.

If you have capacity: do it in a VM first.

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.

For the most part, it’s pretty painless. Unless you have a super complex setup you’ll be fine.