My favourite - and I’ve gotten into arguments with people about this who clearly never just tried it to see what happens - is it never executes things with the shell you think it will.
So many people assume that just because their script says at the top that cron is going to run it in bash. The reality is without ALSO setting SHELL=/bin/bash in the crontab file, you’re getting your system’s lowest-common-denominator shell (ash/dash/sh/whatever other gross abomination).
So much time wasted debugging. And I’m generally pretty good at avoiding shell-specific syntax, I’ve seen the abominations of shell scripts some people write.
The one thing I do wish systemd timers offered is cron syntax backwards compatibility, rather than just its ISO8601-style time patterns. An every-5-minutes job that used to be */5 * * * * is now OnCalendar=*-*-* *:0/5:0 and I’m just not sure that syntax is universally an improvement.














They’re waiting for you Gordon… In the test chamber