There's no need to be embarrassed about your lack of knowledge Jimmy. I didn't know any of this until I learned it either! :) So thanks for allowing me the opportunity to enlighten you (and other passers by that might be reading this). You can help us too by giving feedback and asking questions about anything that you don't understand or doesn't make sense.. One of the biggest issues we have when writing docs and sharing info is curse of knowledge.

Also, not sure if you saw my other post? You should be able to upgrade ZoneMinder to v1.36.x, just not to the latest version.

Anyway, to get you started on, have a read of these doc pages:

• How TurnKey Linux relates to Debian
• How to upgrade an appliance (overview)

If you wanted to try the TKLBAM data migration method, I would recommend testing on a local VM first. I.e. install the newer TurnKey version to a VM (install from ISO). Then restore your backup and see how it goes.

Having said that, the data migration method is likely more suited to when you're running TurnKey in a VM. With a bare metal install such as yours, I suspect that a Debian "in place" upgrade would be a better way to go.

Before you start

SSH

Personally, I think the best way to work with a server is via SSH. Obviously it's extremely useful to have direct access to it's terminal - e.g. for install and for network and early boot troubleshooting. Otherwise IMO working via SSH from a desktop system is preferable. It makes documenting your steps easier (e.g. dry run in a VM) and also makes following instructions online easier (both use cases: copy/paste FTW!). It's also really useful for finding info when you hit errors (again copy/paste - this time into google).

I'm a Linux user so OpenSSH client (i.e. 'ssh' CLI tool) comes by default. It ships with Mac OSX too. I note that Windows 11 also ships with OpenSSH client preinstalled by default. It's also pretty easy to install yourself in Windows 10. On Windows though you also have other choices, such as PuTTY or WinSCP. Personally I prefer the terminal ssh client, but YMMV.

Dry run in a VM

If you plan to do an "in place" upgrade, especially as the first time you attempt this, I strongly recommend doing a dry run in a VM first. I.e. install v16.1 ZoneMinder into a VM and then step through the upgrade. Because it will be a fresh TurnKey install and it won't have your data it's not an exact analog - but should allow you to get an understanding of the process and work through any issues that you might hit. I highly recommend documenting this as you go. You can then just re-run the steps later when you do it for real.

Backups and Snapshot

Backups are important. The reality is that data loss is a matter of when, not if. So if you care about your data, you are, at the very least manually taking backups of anything important. Automated backups are really the only way to be sure. And backups also need to be tested. It is said that just like untested code is always buggy, untested backups are unreliable. Sorry, I'm ranting a bit. My point was that you should already have backups and if you don't, now is the time to sort that out!

Snapshots are considered backups by some and I don't think it's a completely unreasonable argument. Although personally, I like having a backup, where the data is separated from the underlying OS - generally not possible in a snapshot. However, when doing something as potentially destructive as a major OS upgrade I think a snapshot is a quicker way to get back to exactly where you were before you started.

Snapshots are usually super easy when using a VM (it should be a feature of the VM software). On a bare metal install it's not quite so easy. Although still possible. I suggest taking a clone of your system using a tool such as Clonezilla.

The "in place" upgrade

The Debian 11/Bullseye Release Notes is the Debian upgrade "bible". Having said that, unless you're really interested, I wouldn't bother reading all of it. In fact I wouldn't even recommend reading much of it unless you want to understand the process much more. It goes into extreme detail and covers desktop systems that are completely irrelevant as a TurnKey user. The chapter that is likely most useful is Chapter 4. Upgrades from Debian 10 (buster). Like the rest of the release notes, it goes into lots of detail and some steps will be redundant or irrelevant, but should be relatively solid advice.

My advice is to skim through Chapter 4 from the release notes (as linked above) and then google for "debian cli upgrade buster bullseye". There should be plenty of more straight forward tutorials on how to actually do the upgrade via CLI (without the minutia).

Last words and a hint

Upgrading TurnKey v16.x (based on Debian 10/Buster) to a Debian 11/Bullseye base should go pretty smoothly. When I upgraded my desktop (I run Debian as my main PC) I spent nearly twice as long reading release notes than it actually took to do the upgrade. But as a novice it's possible you may hit issues. If you follow my advice and do a dry run in a VM first and ask if you hit any issues, or have any questions, then before you even start for real, you should have a pretty good grounding in what to expect. Then if you ensure you have both backups and a snapshot, then I don't think you can go too far wrong. Worst case, restore right back to where you are now.

One point I'm sure you'll hit - when you upgrade the TurnKey sources.list entries from 'buster' to 'bullseye', you'll get a key error when you run 'apt update'. To fix that (or to preempt it now you know to expect it), you'll need to download the keys from GitHub:

_url="https://raw.githubusercontent.com/turnkeylinux/common/master/overlays/bootstrap_apt"
for _repo in main security testing; do
    _key="usr/share/keyrings/tkl-bullseye-$_repo"
    curl "$_url/${_key}.asc" | gpg --dearmor > "/${_key}.gpg"
done

Good luck and please don't hesitate to post back at any point with any questions. Please keep us posted on how you go with it all regardless, but especially if you have success! :)