The evils which have never happened

I found this stupidly useful shortcut inside of cron.  Generally crontab entries look like this:

* * * * *  username dosomething

With the * corresponding to minute, hour day of month, month, day of week.  But cron also has a couple shortcuts that are useful for general system maintenance.  Specifically @reboot which replaces  ALL of the “*”‘s and will be run after each system reboot.  There is also a system wide directory under  /etc called cron.d which is wonderfully useful for package management because you can drop custom package cron jobs into the directory without directly editing the crontab file.

All of this information is well know among the Unix community as a whole and fairly well mentioned is about 10,000 different places.  Here is something that isn’t quite as easy to find but still ends up being pretty important…

File entries in cron.d cannot have a period in their name…. no file extension… no period separator… NOTHING… otherwise cron simply doesn’t run the file!!!

I just about killed myself debugging this one over the last two days. </crying>  Now if you will excuse me, I am going to drink my body weight in beer.