Back in the early aughts I was applying as a junior sysadmin for one of those up-and-coming LAMP web-hosting companies here in Vienna. The interviewer was a great, all-around-nice guy and a very experienced sysadmin. All went rather well until he asked me on how I would go about fixing a specific Apache httpd issue.. suffice to say I was still green behind my ears and didn't know about strace and that was pretty much it.

I'm still very grateful that I funked up that interview as otherwise, down the line I maybe wouldn't have gone into systems programming / unix internals as easily.

Julia Evans has a great strace related zine on her website, check it out as well:

http://jvns.ca/blog/2015/04/14/strace-zine/

Also - if you are on MacOS/BSD you should check out the somewhat related dtrace/dtruss, very powerful tools.