Cron and the accompanying crontab is a scheduler. That is, you set the schedule for the programs you want to run at certain times. The instruction is clear enough, except, there is absolutely no instruction about the macro. By that I mean @hourly and others. I really can't find any instruction at all! I know @hourly is present because it is mentioned there. How about other macros? @daily, @weekly seem obvious. How about @minutely? Is that valid? I have no idea.
Here's something else: @reboot.
Yeah, I read that in some instruction pages somewhere, except I don't know how that person know that there is such instruction! It's not mentioned anywhere that I checked! Well, there's only one thing to do, then, isn't it? Try it out and see if the program really runs at booting time.
Strange that the macro is named @reboot. One would think that @boot would be more appropriate. No, I don't know if @boot macro exists. Like I said, there's no documentation that I can find anywhere.