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I have a PS/2 adaptor with a retro mouse and keyboard connected and Debian 12 is doing something different when it is booted up with or without that plugged into a USB port.

Either way, the keyboard and mouse work perfectly, however plugging it in after bootup does not cause this "symptom" to appear whereas if it is plugged into the USB port while the computer is switched off then the computer is booted, the symptom appears.

The symptom is visible in the gui of the power tray icon.

If booted up without the PS/2 connected it looks like this : only brightness of screen

If booted up with the PS/2 connected it looks like this : brightness of screen and brightness of keyboard backlight

It's not the colour of those message boxes, that's just the camera used to take the picture. It's that booting up with that USB plugged in shows a screen brightness adjuster as well as a keyboard backlight adjuster whereas booting up without that plugged in shows only the screen brightness.

The keyboard backlight thing does not work anyway, but this change in the gui depending on what is plugged in upon bootup suggests that something is different, and I believe that that "something" is having side effects and I would like to know what it is.

I'd like to enter a command to write a file upon bootup with and without that plugged in then take the diff of the 2 files.

What is the most appropriate command to generate such a file which would most likely contain in it somewhere whatever is causing this? The 2 files need to be easy to take a diff, so if they are full of time stamps it would make that hard as every line will be different due to the time stamp. It's just going to be unpleasant to try to sift through such large log files manually to try and find what is different.

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As soon as it boots up, run

sudo dmesg > dmesg_no_usb

then plug in the usb device, reboot, and run

sudo dmesg > dmesg_with_usb

you now have two files to compare. For additional information, boot with the usb device not plugged in, plug the usb device in, and then run

sudo dmesg > dmesg_usb_plugged_in_once_booted

You now have files you can diff.

Finally, since I always boot into a bash shell (and examine dmesg there, if needed) and only then do "startx" for xfce or wmaker, I do not know if the X11 startup process is logged in dmesg; you probably will need to look at some X11 logs, and at startup logs generated by your window manager or desktop app (e.g., KDE, Gnome, ...).

I use Debian as well, and have Debian 7, 8, 10, 12, and 13 on various systems, including as schroots.

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  • Thanks, I like the sound of booting into a bash shell, logging in there then maybe starting the desktop environment (in my case Cinnamon), will try that. I was experimenting with lsmod but there was no difference between plugged and not. I see you can get rid of the dmesg timestamp like this dmesg --notime Commented Nov 9 at 11:01
  • I had to use Python to do the diff, diff in the terminal was too messy. Subtracted a set of the lines of each. Then lo and behold : input,hidraw0: USB HID v1.10 Keyboard [CHESEN PS2 to USB Converter] on usb and input,hidraw1: USB HID v1.10 Mouse [CHESEN PS2 to USB Converter] on usb There are actually a lot more things than that which are different, as if this USB woke some things up which were asleep. I'll probably upgrade soon to Debian 13 and maybe some issues will just go away. Commented Nov 9 at 14:24

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