I have checked auth.log and found something interesting. When everything is OK, the log looks like this Jul 15 18:11:02 weihong-pc systemd-logind[870]: New seat seat0. Jul 15 18:11:03 weihong-pc systemd-logind[870]: Watching system buttons on /dev/input/event1 (Power Button) Jul 15 18:11:03 weihong-pc systemd-logind[870]: Watching system buttons on /dev/input/event10 (Video Bus) Jul 15 18:11:03 weihong-pc systemd-logind[870]: Watching system buttons on /dev/input/event0 (Power Button) Jul 15 18:11:05 weihong-pc lightdm: PAM unable to dlopen(pam_kwallet.so): /lib/security/pam_kwallet.so: cannot open shared object file: No such file or directory Jul 15 18:11:05 weihong-pc lightdm: PAM adding faulty module: pam_kwallet.so Jul 15 18:11:05 weihong-pc lightdm: pam_unix(lightdm-greeter:session): session opened for user lightdm by (uid=0) Jul 15 18:11:05 weihong-pc systemd-logind[870]: New session c1 of user lightdm. Jul 15 18:11:05 weihong-pc systemd-logind[870]: Linked /tmp/.X11-unix/X0 to /run/user/104/X11-display. Jul 15 18:11:05 weihong-pc lightdm: pam_ck_connector(lightdm-greeter:session): nox11 mode, ignoring PAM_TTY :0 Jul 15 18:11:08 weihong-pc lightdm: PAM unable to dlopen(pam_kwallet.so): /lib/security/pam_kwallet.so: cannot open shared object file: No such file or directory Jul 15 18:11:08 weihong-pc lightdm: PAM adding faulty module: pam_kwallet.so Jul 15 18:11:08 weihong-pc lightdm: pam_succeed_if(lightdm:auth): requirement "user ingroup nopasswdlogin" not met by user "weihong" Jul 15 18:11:08 weihong-pc dbus[754]: [system] Rejected send message, 7 matched rules; type="method_return", sender=":1.25" (uid=0 pid=1450 comm="/usr/sbin/dnsmasq --no-resolv --keep-in-foreground") interface="(unset)" member="(unset)" error name="(unset)" requested_reply="0" destination=":1.5" (uid=0 pid=939 comm="NetworkManager ") Jul 15 18:11:12 weihong-pc lightdm: pam_unix(lightdm-greeter:session): session closed for user lightdm Jul 15 18:11:12 weihong-pc lightdm: pam_unix(lightdm:session): session opened for user weihong by (uid=0) Jul 15 18:11:12 weihong-pc systemd-logind[870]: New session c2 of user weihong. Jul 15 18:11:12 weihong-pc systemd-logind[870]: Linked /tmp/.X11-unix/X0 to /run/user/1000/X11-display. Jul 15 18:11:12 weihong-pc lightdm: pam_ck_connector(lightdm:session): nox11 mode, ignoring PAM_TTY :0 Jul 15 18:11:14 weihong-pc gnome-keyring-daemon[1622]: Gkm: using old keyring directory: /home/weihong/.gnome2/keyrings Jul 15 18:11:14 weihong-pc gnome-keyring-daemon[1622]: Gkm: using old keyring directory: /home/weihong/.gnome2/keyrings Jul 15 18:11:14 weihong-pc gnome-keyring-daemon[1622]: couldn't set environment variable in session: The name org.gnome.SessionManager was not provided by any .service files Jul 15 18:11:15 weihong-pc polkitd(authority=local): Registered Authentication Agent for unix-session:c2 (system bus name :1.39 [/usr/lib/policykit-1-gnome/polkit-gnome-authentication-agent-1], object path /org/gnome/PolicyKit1/AuthenticationAgent, locale en_US.UTF-8) Jul 15 18:11:14 weihong-pc gnome-keyring-daemon[1622]: message repeated 2 times: [ couldn't set environment variable in session: The name org.gnome.SessionManager was not provided by any .service files] Jul 15 18:11:51 weihong-pc gnome-keyring-daemon[1622]: keyring alias directory: /home/weihong/.gnome2/keyrings After the upgrade, the log looks like: Jul 18 18:11:55 weihong-pc systemd-logind[1176]: New seat seat0. Jul 18 18:11:55 weihong-pc systemd-logind[1176]: Watching system buttons on /dev/input/event1 (Power Button) Jul 18 18:11:55 weihong-pc systemd-logind[1176]: Watching system buttons on /dev/input/event4 (Video Bus) Jul 18 18:11:55 weihong-pc systemd-logind[1176]: Watching system buttons on /dev/input/event0 (Power Button) Jul 18 18:11:58 weihong-pc lightdm: PAM unable to dlopen(pam_kwallet.so): /lib/security/pam_kwallet.so: cannot open shared object file: No such file or directory Jul 18 18:11:58 weihong-pc lightdm: PAM adding faulty module: pam_kwallet.so Jul 18 18:11:58 weihong-pc lightdm: pam_unix(lightdm-greeter:session): session opened for user lightdm by (uid=0) Jul 18 18:11:58 weihong-pc systemd-logind[1176]: New session c1 of user lightdm. Jul 18 18:11:58 weihong-pc systemd-logind[1176]: Linked /tmp/.X11-unix/X0 to /run/user/104/X11-display. Jul 18 18:11:58 weihong-pc lightdm: pam_ck_connector(lightdm-greeter:session): nox11 mode, ignoring PAM_TTY :0 Jul 18 18:12:03 weihong-pc lightdm: PAM unable to dlopen(pam_kwallet.so): /lib/security/pam_kwallet.so: cannot open shared object file: No such file or directory Jul 18 18:12:03 weihong-pc lightdm: PAM adding faulty module: pam_kwallet.so Jul 18 18:12:03 weihong-pc lightdm: pam_succeed_if(lightdm:auth): requirement "user ingroup nopasswdlogin" not met by user "weihong" Jul 18 18:12:06 weihong-pc dbus[1061]: [system] Rejected send message, 7 matched rules; type="method_return", sender=":1.22" (uid=0 pid=1338 comm="/usr/sbin/dnsmasq --no-resolv --keep-in-foreground") interface="(unset)" member="(unset)" error name="(unset)" requested_reply="0" destination=":1.11" (uid=0 pid=1239 comm="NetworkManager ") Jul 18 18:12:10 weihong-pc lightdm: pam_unix(lightdm-greeter:session): session closed for user lightdm Jul 18 18:12:10 weihong-pc lightdm: pam_unix(lightdm:session): session opened for user weihong by (uid=0) Jul 18 18:12:10 weihong-pc systemd-logind[1176]: New session c2 of user weihong. Jul 18 18:12:10 weihong-pc systemd-logind[1176]: Linked /tmp/.X11-unix/X0 to /run/user/1000/X11-display. Jul 18 18:12:10 weihong-pc lightdm: pam_ck_connector(lightdm:session): nox11 mode, ignoring PAM_TTY :0 Jul 18 18:13:22 weihong-pc systemd-logind[1176]: Failed to issue method call: Unknown unit: