Question

What's your worst mistake / best lesson learned administering a server?

“Fail fast, learn fast” has become a bit of a mantra for entrepreneurs these days. While they’re not always as forgiving when their website is down, those of us on the technical side learn from our mistakes too.

We’ve all fat fingered a command or two, but what have you learned from it? Share your stories, not just of your worst sysadmin mistakes, but also of the best lessons you’ve learned from them.

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Accidentally dropped a production database instead of a development one. Site naturally came crashing down.

Since then I double/triple check which server I’m connecting to before doing anything destructive.

I was rolling my own self-scaling cloud earlier this year via a nodejs script that spun up X number of droplets using the Digital Ocean API. In synchronous code, it would have been a simple for loop, but this was async and parallel. But I had set X to a fairly modest number (5) so I didn’t think much could go awry. First test, it becomes clear I wasn’t incrementing my loop correctly, and in the two seconds it took me to realize my mistake and hit Ctrl+C, I’d already created over 200 droplets on Digital Ocean! Luckily, I’d already created a script to mass delete droplets, so I was able to correct my mistake within a few minutes. Since then I have always implemented “dry run” versions of any script to test the control flow logic before I implement the actual commands.

Typing rm -rf /* instead of rm -rf ./*… Taught me to be far more carful when using sudo and globs.