Printer jobs can not be stopped

Recently I had one of the most frustrating experiences with my printer.

I sent a some print jobs to my Canon Pixus iP3100 printer, but then realized there was a problem with the layout, and so I wanted to kill the print jobs. I went to this interface:

However, pressing the stop button, marked with the square, did nothing.

I tried everything I could think of to kill the print jobs. I tried restarting the printer. I rebooted the computer. I hit "reset" on the printer. I tried killing any printer related tasks in the task manager.

No matter what I did, though, the same jobs were in the queue, and the only way in the end that I was able to get past them was to have them all run through to the end.

Is this a bug, or is there some other aspect to this that I am missing?

Open the terminal and type lprm. This will clear the print queue and thus stop the printing.

"lpq -a" will show you jobs on all printers (without the -a it will only show jobs on the default printer).

The third field of the output will be the job number, which you can use with "lprm" to cancel a specific job.

Here's an example. PDF is my default printer, but not the one I sent my jobs to:

[$] lpq
PDF is ready no entries

[$] lpq -a
Rank Owner Job File(s)
Total Size active (null) 151 untitled
1853440 bytes 1st (null) 153 untitled
100352 bytes

[$] lprm 153

[$] lpq -a
Rank Owner Job File(s)
Total Size active (null) 151 untitled
1853440 bytes

lprm did not work for me - there must be something strange about my Ubuntu install.

However, typing cancel -a in a terminal worked fine.