After updating Arch today I found I could no longer mount usb storage devices – usb sticks. The log shows the device coming up, but then messages from MTP saying:

mtp-probe: bus: 2, device: 5 was not an MTP device

I have seen this before. It is irritating, I am doing something else, my head full of whatever it is, and suddenly usb sticks won’t mount.

Did some reading, some people reported that old udev rules for the libmtp library could be a problem. Libmtp is about the Media Transfer Protocol, which I believe to be involved with automatically recognizing when you plug in your phone that maybe you want to transfer stuff from it (pictures). I’m not sure. I don’t do it.

I removed from /lib/udev/rules.d the 69-libmtp.rules and squirreled them away somewhere I am sure I will forget, and rebooted, and now once again I can recognize usb devices.

When I do the pacman updates, sometimes it claims I have local changes to config files which I don’t remember changing. It is vaguely possible that today when I did the pacman update, that it mentioned finding libmtp rules and asked if I wanted to replace them or keep them. I don’t remember doing that, at all, nor do I ever remember modifying the libmtp rules. Doesn’t mean I never did. And my practice, usually, when pacman asks is to leave in place any config that I already have there, so I would have answered to leave it in place.

So it could be my fault.

But at least now I know what to do.