Just fifteen minutes ago I realized that my script to refactor the primary file server (newly converted to ZFS) into more sensible datasets had an irritating detail wrong (a path element was being duplicated in some paths).
I said to myself "oh, I'll just roll that whole thing back to the snapshot I made 30 minutes ago".
Then I go "zfs list -t snapshot" and discover that my snapshot was holding onto 0 GB because I forgot the -r switch to make the snapshot recursive.
Oh, well. By some impossible-to-separate mixture of good management and good fortune, it turns out I had a set of (different) snapshots from the last two days covering all datasets in questions. I lost very little work (only scripts were executed against these datasets and I still have all the scripts).
My real screw up?
Back in my second co-op workterm job, I managed not to notice that a system I was backing up changed the order of the listed drives between two very similar screen requests that I made almost immediately one after the other. Unfortunately, on the second pass I selected the active system drive as the recipient of the system backup, picking from the position in the menu where the desired destination drive had appeared moments before.
I had become accustomed to my home system being deterministic in the order it listed things. My bad.
This is back at the very beginnings of the 4.77 MHz era, so my PC was actually not yet what we now know as a "PC" (its father had an S-100, and its mother had a itty-bitty CRT).
Thirty years later I still can't type dd of=/dev/ada3 without making three trips to the metaphorical bathroom.
Whenever I type a disk-level dd command, I leave the sudo off, until after the third proof-read and several console consultations in which at least two different programs give me the same view of the drive name.
In dollar costs I couldn't say. In psychic cost, it's indelibly etched onto my permanent record.
I had a co-worker once (EEng) who claimed that as a junior intern during the late 1990s back when laser gear for fiber optics was all the rage, he routinely fried extremely delicate $2000 DUTs while the old hands just shrugged their shoulders. Dotcom dollars. Who really gave a fuck? It was considered barely worse than ruining a nice chair.
A good workmanlike book? It is to SF what The Lord of the Rings is to fantasy, and one of the greatest pieces of world creation ever written.
Now the programmers in the audience could probably think of like 10 different specific things that could be coded into the system to prevent that from happening, but this company didn't. Which really isn't too surprising. I asked one of the devs on the ground systems team if the ground systems was using GMT or UTC. His answer was "What's the difference?" I was able to infer from his answer that it was most likely GMT, and that did appear to be the case. Somewhere deep in the bowels of the system there was presumably some piece of code written by an Indian contractor with a math degree adjusting times for leap seconds, but it wasn't in any code that anyone knew about.
The early history of that company read like a Monty Python sketch. The first satellite exploded on the launch pad. The second satellite fell over and then exploded. The third satellite burned down, fell over, exploded and then sank into the swamp. The forth satellite got into orbit and was promptly bricked by sending the wrong version of Windows(!) to it. To be fair they only had to do that because they launched it with the wrong version of Windows(!!) in the first place. One would think that ANY version of Windows would be the wrong version of Windows to shoot into space, but that's why you're not the head of a billion dollar satellite company.
Mostly I make my career out of fixing other people's tech mistakes. Which is not something that uni taught me how to do. Man I'm glad I got out of that place before I ran up any significant student debt. Did I mention I trash talked a uni on a news blag website?
More to the point, the skills I've picked up skydiving are not ones that are going to go away at any point in my life. Even if I quit the sport, I'd still be able to hop into the wind tunnel at any point and fly. Contrast that with the ability to, let's say, run Molten Core. Anyone in a guild who did that during vanilla WoW spent way more time learning how to do that than I did skydiving. Keep in mind that my actual freefall time at the time I got my A license was less than an hour. And that's with wind tunnel time. The hypothetical guild probably spent several times that much time wiping on trash to get to the first boss. Three years later, I'm still building on my skydiving skills. Three years later, the hypothetical guild's shiny purple crap has been obsolete for three expansions and if anyone runs Molten Core anymore, it's 1 or 2 people going for some vanity drop. That's a significantly less rewarding experience, and I know that first-hand.
MESSAGE ACKNOWLEDGED -- The Pershing II missiles have been launched.