Public bug reported:
On Ubuntu 26.10, the GDM greeter never offers fingerprint authentication, even
when fingerprints are enrolled and working correctly. Screen lock inside a
session works fine, but the login screen at boot / after logout only accepts a
password.
gnome-shell in the greeter repeatedly fails to start biometric
verification:
gnome-shell[2432]: Failed to start gdm-authd verification for user:
GDBus.Error:org.gnome.DisplayManager.SessionWorker.Error.ServiceUnavailable:
GDBus.Error:org.gnome.DisplayManager.SessionWorker.Error.ServiceUnavailable:
PAM service gdm-authd was not found
The PAM service "gdm-authd" is required by gnome-shell 51, but the gdm3
package for Ubuntu 26.10 does not ship it, nor any binary that would provide
it:
$ dpkg -L gdm3 | grep -E 'bin/|sbin/'
/usr/bin/gdm-config
/usr/sbin/gdm3
$ dpkg -L gdm3 | grep pam.d
/etc/pam.d/gdm-autologin
/etc/pam.d/gdm-fingerprint
/etc/pam.d/gdm-launch-environment
/etc/pam.d/gdm-password
/etc/pam.d/gdm-smartcard-pkcs11-exclusive
/etc/pam.d/gdm-smartcard-sssd-exclusive
/etc/pam.d/gdm-smartcard-sssd-or-password
There is no /etc/pam.d/gdm-authd and no gdm-authd binary anywhere on the
system:
$ find / -name "gdm-authd*" -not -path "/proc/*"
(no results)
Note that gdm3 does ship /etc/pam.d/gdm-fingerprint, which contains
"auth required pam_fprintd.so", but gnome-shell does not use that service for
its biometric verification flow - it specifically requests "gdm-authd".
** Affects: gdm3 (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2171275
Title:
Fingerprint authentication never offered in GDM greeter on Ubuntu
26.10: missing PAM service "gdm-authd"
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