dnf system-upgrade reboot stalled after reboot (KDE F26->F27)

Tuesday, 15 May 2018

I followed the instruction from
http://fedoraproject.org/wiki/DNF_system_upgrade
to upgrade a system from F26 to F27. Everything seemed to work
correctly (all packages installed and checked), then the system
rebooted on F27. I saw the fedora icon now surrounded by a white
square.
But it is now stalled with only this on the screen:
[   6.196960] tpm tpm0: tpm_try_transmit: tpm_send: error -62.

Apparently, I can access the system with ssh. Looking at the journal,
I see a lot of red (many more such lines in the log):

May 15 14:14:50 beta sddm-helper[4245]: PAM adding faulty module:
/usr/lib64/security/pam_elogind.so
May 15 14:14:50 beta audit[4245]: USER_ACCT pid=4245 uid=0
auid=4294967295 ses=4294967295
subj=system_u:system_r:xdm_t:s0-s0:c0.c1023 msg='op=PAM:accounting
grantors=pam_permit acct="sddm" exe="/usr/libe
May 15 14:14:50 beta audit[4245]: USER_AUTH pid=4245 uid=0
auid=4294967295 ses=4294967295
subj=system_u:system_r:xdm_t:s0-s0:c0.c1023 msg='op=PAM:authentication
grantors=pam_permit acct="sddm" exe="/usr/
May 15 14:14:50 beta sddm-helper[4245]: PAM unable to
dlopen(/usr/lib64/security/pam_elogind.so):
/usr/lib64/security/pam_elogind.so: cannot open shared object file: No
such file or directory
May 15 14:14:50 beta sddm[1233]: QProcess: Destroyed while process
("/usr/libexec/sddm-helper") is still running.
May 15 14:14:49 beta sddm-helper[4240]: PAM adding faulty module:
/usr/lib64/security/pam_elogind.so
May 15 14:14:49 beta audit[4240]: USER_ACCT pid=4240 uid=0
auid=4294967295 ses=4294967295
subj=system_u:system_r:xdm_t:s0-s0:c0.c1023 msg='op=PAM:accounting
grantors=pam_permit acct="sddm" exe="/usr/libe
May 15 14:14:49 beta audit[4240]: USER_AUTH pid=4240 uid=0
auid=4294967295 ses=4294967295
subj=system_u:system_r:xdm_t:s0-s0:c0.c1023 msg='op=PAM:authentication
grantors=pam_permit acct="sddm" exe="/usr/
May 15 14:14:49 beta sddm-helper[4240]: PAM unable to
dlopen(/usr/lib64/security/pam_elogind.so):
/usr/lib64/security/pam_elogind.so: cannot open shared object file: No
such file or directory
May 15 14:14:49 beta sddm[1233]: QProcess: Destroyed while process
("/usr/libexec/sddm-helper") is still running.
May 15 14:14:49 beta sddm-helper[4235]: PAM adding faulty module:
/usr/lib64/security/pam_elogind.so
May 15 14:14:49 beta audit[4235]: USER_ACCT pid=4235 uid=0
auid=4294967295 ses=4294967295
subj=system_u:system_r:xdm_t:s0-s0:c0.c1023 msg='op=PAM:accounting
grantors=pam_permit acct="sddm" exe="/usr/libe
May 15 14:14:49 beta audit[4235]: USER_AUTH pid=4235 uid=0
auid=4294967295 ses=4294967295
subj=system_u:system_r:xdm_t:s0-s0:c0.c1023 msg='op=PAM:authentication
grantors=pam_permit acct="sddm" exe="/usr/
May 15 14:14:49 beta sddm-helper[4235]: PAM unable to
dlopen(/usr/lib64/security/pam_elogind.so):
/usr/lib64/security/pam_elogind.so: cannot open shared object file: No
such file or directory
May 15 14:14:49 beta sddm[1233]: QProcess: Destroyed while process
("/usr/libexec/sddm-helper") is still running.
May 15 14:14:49 beta sddm-helper[4230]: PAM adding faulty module:
/usr/lib64/security/pam_elogind.so
May 15 14:14:49 beta audit[4230]: USER_ACCT pid=4230 uid=0
auid=4294967295 ses=4294967295
subj=system_u:system_r:xdm_t:s0-s0:c0.c1023 msg='op=PAM:accounting
grantors=pam_permit acct="sddm" exe="/usr/libe
May 15 14:14:49 beta audit[4230]: USER_AUTH pid=4230 uid=0
auid=4294967295 ses=4294967295
subj=system_u:system_r:xdm_t:s0-s0:c0.c1023 msg='op=PAM:authentication
grantors=pam_permit acct="sddm" exe="/usr/
May 15 14:14:49 beta sddm-helper[4230]: PAM unable to
dlopen(/usr/lib64/security/pam_elogind.so):
/usr/lib64/security/pam_elogind.so: cannot open shared object file: No
such file or directory
May 15 14:14:49 beta sddm[1233]: QProcess: Destroyed while process
("/usr/libexec/sddm-helper") is still running.
May 15 14:14:49 beta sddm-helper[4225]: PAM adding faulty module:
/usr/lib64/security/pam_elogind.so
May 15 14:14:49 beta audit[4225]: USER_ACCT pid=4225 uid=0
auid=4294967295 ses=4294967295
subj=system_u:system_r:xdm_t:s0-s0:c0.c1023 msg='op=PAM:accounting
grantors=pam_permit acct="sddm" exe="/usr/libe
May 15 14:14:49 beta audit[4225]: USER_AUTH pid=4225 uid=0
auid=4294967295 ses=4294967295
subj=system_u:system_r:xdm_t:s0-s0:c0.c1023 msg='op=PAM:authentication
grantors=pam_permit acct="sddm" exe="/usr/
May 15 14:14:49 beta sddm-helper[4225]: PAM unable to
dlopen(/usr/lib64/security/pam_elogind.so):
/usr/lib64/security/pam_elogind.so: cannot open shared object file: No
such file or directory
May 15 14:14:49 beta sddm[1233]: QProcess: Destroyed while process
("/usr/libexec/sddm-helper") is still running.
May 15 14:14:49 beta sddm-helper[4220]: PAM adding faulty module:
/usr/lib64/security/pam_elogind.so

Thanks,

F