Tinkering is all fun and games, until it's 4 am, your vision is blurry, and thinking straight becomes a non-option, or perhaps you just get overly confident, type something and press enter before considering the consequences of the command you're about to execute... And then all you have is a kernel panic and one thought bouncing in your head: "damn, what did I expect to happen?".
Off the top of my head I remember 2 of those. Both happened a while ago, so I don't remember all the details, unfortunately.
For the warmup, removing PAM. I was trying to convert my artix install to a regular arch without reinstalling everything. Should be kinda simple: change repos, install systemd, uninstall dinit and it's units, profit. Yet after doing just that I was left with some PAM errors... So, I Rdd-ed libpam instead of just using --overwrite. Needless to say, I had to search for live usb yet again.
And the one at least I find quite funny. After about a year of using arch I was considering myself a confident enough user, and it so happened that I wanted to install smth that was packaged for debian. A reasonable person would, perhaps, write a pkgbuild that would unpack the .deb and install it's contents properly along with all the necessary dependencies. But not me, I installed dpkg. The package refused to either work or install complaining that the version of glibc was incorrect... So, I installed glibc from Debian's repos. After a few seconds my poor PC probably spent staring in disbelief at the sheer stupidity of the meatbag behind the keyboard, I was met with a reboot, a kernel panic, and a need to find another PC to flash an archiso to a flash drive ('cause ofc I didn't have one at the time).
Anyways, what are your stories?
I can't even remember how I did this, but overwriting the partition table on the main production server at our small startup (back when "the server" would usually live on the premises of the startup). I remember my boss starting to hyperventilate from panic while I reconstructed it from memory / notes, and all the filesystems came back and he calmed down.
Same job, they gave me a little embedded-systems unit for me to use to build a prototype on. I hooked it up, nothing worked. I brought it back to them.
Hey, this one doesn't work.
Huh... that's weird, it was working before. Did you break it?
I don't think so. Can I have one that works?
They literally told me, as they were handing me the second one: Okay, here's another one. Don't break it.
I figured it out literally seconds after breaking the second one... I was hooking it up to 12 volts of power when it needed 5. Second dead computer. Explaining that and that I needed a third one now was fun.
Had something similar several years ago: prototype stopped working for some reason, one of the hardware engineers and I were troubleshooting on a second prototype, and we exploded a large capacitor... The rest of the team were not amused that we destroyed 2 out of 3 working prototypes within 10 minutes.