Is it a PAM or KDE behavior? At first, I thought this might be due to the default value of 3 of the max-tries option (see man pam_fprintd). However, attempting to set max-tries=10 in both /etc/pam.d/plasmalogin and /etc/pam.d/kde-fingerprint (both files copied from /usr/lib/pam.d) made no difference. Logging in with a password works normally.
The issue is reproducible by moving the mouse or pressing a key that doesn’t input a character (e.g., Shift key) after the login prompt disappears. Repeating this action multiple times - each time after the prompt has vanished - shows the behavior. The explanatory text below the input field regarding the option to log in using a fingerprint also disappears by the fourth attempt.
Own lines in /etc/pam.d/plasmalogin:
# Locally set by admin for fingerprint recognition:
auth sufficient pam_unix.so try_first_pass
auth sufficient pam_fprintd.so max-tries=10 timeout=2
# proposed parameters from arch wiki not used on this computer:# likeauth nullok
# Default contents from /usr/lib/pam.d/plasmalogin:
...
Expanded line in /etc/pam.d/kde-fingerprint:
# max-tries added on this computer:
-auth required pam_fprintd.so max-tries=10
Are you talking about screen lock or the login page (either plasma-login or sddm), They look the same/similar but are two different things. I’m assuming KDE, but other particulars you left out of your post. At least provide your system parameters from inxi -zv8
As @sweasyf said, plasma-login-manager and kscreenlocker are two very different components. pam-related settings for the first one have no effect on the second one, and vice versa.
I also didn’t read your post fully, you are mentioning fingerprint issues, but not password issues. I don’t use fingerprint, so I won’t be able to help with that issue. I’ll keep watching so I can learn something.
Yes I’m aware of that. But I didn’t find any fingerprint config items for kscreenlocker, but only for PAM files. And because there is the general KDE pam file name pam_kde-fingerprint I made that try.
Well, I don’t have a fingerprint reader and I have no such file on my system, but I suspect that it does really only work on account of the login procedure, not on account of unlocking the screen.
The good news is: it works. The phenomenon only occurs with careless use, when moving the mouse and not directly make an input to the screensaver - for instance due to an intervening phone call - or three of them). It is a minor cosmetic issue. If it isn’t a configuration thing, it might be of interest for KDE developers.
Perhaps you can file a bug report at bugs.kde.org then. You’ll have to register an account first, and you may also not get an immediate response from the developers after filing your bug, but then at least it’s on record.
Apparently, an additional time frame (timeout=x) must also be defined. The default of 30 seconds was to short. I set it to ‘-1’ and will observe the behavior:
(According man pam_fprintd: Use a negative value to set no limit at all, so that fingerprint authentication will be always active while this module is loaded)
Addendum on August 28, 2026: KDE developers do not recommend the ‘timeout=-1’ solution, as it could lead to the fingerprint sensor overheating. Instead, they are aiming for a general improvement in fingerprint recognition (including for the plasma-login-manager, ‘Please improve Plasma Login Manager for fingerprint login - Development - KDE Discuss’).
Mod edit:Consecutive posts merged.
If there are no intervening replies, please edit your previous post instead to add further information. Cheers!
