I reproduced the second part of the problem (screen locks and fails to unlock) after upgrading from 16.04 to 18.04 and before restarting the machine (finish the upgrade, close the upgrader and wait until the screen saver goes off)
The following lines are displayed in the journal:
juil. 04 09:27:07 ubuntu compiz[1692]: PAM unable to dlopen(pam_unix.so): /lib/security/pam_unix.so: Ne peut ouvrir le fichier d'objet partagé: Aucun fichier ou dossier de ce type
juil. 04 09:27:07 ubuntu compiz[1692]: PAM adding faulty module: pam_unix.so
juil. 04 09:27:07 ubuntu compiz[1692]: PAM unable to dlopen(pam_systemd.so): /lib/security/pam_systemd.so: Ne peut ouvrir le fichier d'objet partagé: Aucun fichier ou dossier de ce type
juil. 04 09:27:07 ubuntu compiz[1692]: PAM adding faulty module: pam_systemd.so
However I didn't reproduce the "lock screen during upgrade" issue even with a config prompt during upgrade.
I reproduced the second part of the problem (screen locks and fails to unlock) after upgrading from 16.04 to 18.04 and before restarting the machine (finish the upgrade, close the upgrader and wait until the screen saver goes off)
The following lines are displayed in the journal: pam_unix. so): /lib/security/ pam_unix. so: Ne peut ouvrir le fichier d'objet partagé: Aucun fichier ou dossier de ce type pam_systemd. so): /lib/security/ pam_systemd. so: Ne peut ouvrir le fichier d'objet partagé: Aucun fichier ou dossier de ce type
juil. 04 09:27:07 ubuntu compiz[1692]: PAM unable to dlopen(
juil. 04 09:27:07 ubuntu compiz[1692]: PAM adding faulty module: pam_unix.so
juil. 04 09:27:07 ubuntu compiz[1692]: PAM unable to dlopen(
juil. 04 09:27:07 ubuntu compiz[1692]: PAM adding faulty module: pam_systemd.so
However I didn't reproduce the "lock screen during upgrade" issue even with a config prompt during upgrade.