It turns out this happens a lot, and it’s (likely) not a Linux problem.
The symptom: Suddenly, randomly, some of the keyboard will stop working. Usually this happens in clusters. Perhaps some of the number keys stop working. Perhaps some of the qwerty row. Sometimes the shift key stops working. It could be anything.
The problem is either hardware or software. Here’s how to easily determine which.
- Reboot and get into the BIOS (use F2, F1, whatever special key for your machine).
- Find a place where you can enter text. The admin password field is an option.
- Try to enter text with the keys that weren’t working.
- If the keys work, then it is a software problem.
- If the keys still do not work, then it’s a hardware problem.
- Exit without saving!
Hardware
I’ll start with hardware, because that’s probably the problem. (Especially with Linux; blaming drivers is such a Windows thing to do, isn’t it….)
Easiest fix: clean the keyboard. Use a can of compressed air with a straw; you know the ones. Hold down one of the errant keys and spray air under the top as best you can. See if that does it. (Some warn that this might jiggle debris around and make things worse, so proceed with caution, as always.) If this doesn’t do it, invert the machine and gently tap the keys as you would when typing. In this case, gravity will try to pull any bits out. Finally, you can pop off an errant key and spray air directly around under the top.
Did that work? No? Well, things get more complicated.
Slightly more difficult fix: reseat the ribbon cable. (Unless you’re lucky enough to be using an old ThinkPad where taking the keyboard out is an absolute cinch! But then, if you’re using an old ThinkPad, you’re probably not having keyboard problems (those were the best laptop keyboards ever made. Full stop.))
To reseat the keyboard ribbon cable, you have to get into the machine. This will vary from model to model, but it probably involves removing screws. Do that and find the ribbon cable and reseat it.
Lots of people report success with this technique. But notice something: to do this, you have to invert the laptop and, voila! Gravity and jiggling very well might dislodge debris as in the Easiest Fix. (I struggle with the ribbon cable solution. It’s either seated correctly or not. How could this possibly affect Shift-9, for example? It just doesn’t add up. If you can think of a way that it does add up, please leave a comment. (Haha. Fuck comments.))
While you’re at it, some recommend doing a power cycle. This means disconnecting the battery and pressing the power button for anywhere from 30 seconds to an hour. This will discharge any weird built-up static or whatever. Plausible solution, but I bet it doesn’t help!
If you’ve done these things and the symptoms persist, then you might have drawn the short straw and gotten a munted keyboard. It happens. These are fiddly things, and nobody’s perfect. You might just be staring down some new hardware.
(This happened to me; ultimately, it was a glitch in the actual hardware; there was nothing to be done outside of replacing.)
Software
Uh. If you’re using Linux, then, reinstall the driver? No? That isn’t really a thing. But what I can recommend is updating everything responsibly. The drivers are part of the kernel, so at this point, you’re monkeying with that kind of thing, and that’s not for everybody. (It’s also very likely not your problem. If one key works and one key doesn’t, then clearly the driver works — because that one freaking key works!)
If none of this works and you’re in a real pinch, then plug in a USB keyboard.
Seek professional help.