I’ve got an HP Deskjet printer attached to my computer that inexplicably stopped working. Since the printer is housed on a sliding shelf inside my desk and the power light was still on, I immediately began trying to figure out what might have gone wrong with the software. So I turned debugging on and somewhere in the middle of the debug stream, was a line that basically read “Unable to open device.”
Hmmm. What could that mean? I had initially thought the problem was with one of the many layers of software between my on-screen page and the device driver. This error message indicated something much more fundamental. Well, I’d had an issue with the fan and there had been some power blips recently, perhaps the USB cable had disconnected from the computer or I had a bad USB port.
So I check the back of the computer and the USB cable is connected. Next, I switch the cable to another port. But I still getting the same error. Now, I figure I’ll just delete the printer from CUPS and try to reinstall it (This is not the recommended way to fix a printer connected to a Linux box. But it wasn’t working anyway, so I figured I had little to lose.) Now I discover that CUPS can’t find the printer, so I restart cups and try again.
Still nothing.
How can that be? Toggle the printer power; restart CUPS; try to find the printer again.
Same result.
Alright, time to look at the back of the printer.
The USB cable came unplugged from the back of the printer. Grrrr. Stupid bad assumptions. From there, I had everything running properly again in less than 5 minutes.
I’m blaming the kids for this one. They did … something … somewhere along the way. I know it.