Thanks Davide. Since my original post, I applied the latest CentOS updates, rebooted and now it appears broken for good. The server has been up for well over an hour and AD is still busted. So you are right, I must have gotten lucky after my previous reboot.
Here is the output from the command you gave:
Apr 13 15:48:16 nsdc-trs80.kuntzilla.com systemd[1]: Started Login Service.
Apr 13 15:48:16 nsdc-trs80.kuntzilla.com systemd-networkd[22]: host0 : Cannot configure IPv4 forwarding for interface host0: Read-only file system
Apr 13 15:48:16 nsdc-trs80.kuntzilla.com systemd-networkd[22]: host0 : Cannot configure IPv6 forwarding for interface: Read-only file system
Apr 13 15:48:16 nsdc-trs80.kuntzilla.com systemd-networkd[22]: Enumeration completed
Apr 13 15:48:16 nsdc-trs80.kuntzilla.com systemd[1]: Started Network Service.
Apr 13 15:48:16 nsdc-trs80.kuntzilla.com systemd[1]: Reached target Network.
Apr 13 15:48:16 nsdc-trs80.kuntzilla.com systemd[1]: Starting Network.
Apr 13 15:48:16 nsdc-trs80.kuntzilla.com systemd[1]: Started Samba domain controller daemon.
Apr 13 15:48:16 nsdc-trs80.kuntzilla.com systemd[1]: Starting Samba domain controller daemon...
Apr 13 15:48:16 nsdc-trs80.kuntzilla.com systemd[1]: Reached target Multi-User System.
Apr 13 15:48:16 nsdc-trs80.kuntzilla.com systemd[1]: Starting Multi-User System.
Apr 13 15:48:16 nsdc-trs80.kuntzilla.com systemd[1]: Reached target Graphical Interface.
Apr 13 15:48:16 nsdc-trs80.kuntzilla.com systemd[1]: Starting Graphical Interface.
Apr 13 15:48:16 nsdc-trs80.kuntzilla.com systemd-networkd[22]: host0 : gained carrier
Apr 13 15:48:16 nsdc-trs80.kuntzilla.com systemd-networkd[22]: host0 : link configured
Apr 13 15:48:16 nsdc-trs80.kuntzilla.com systemd[1]: Started Update UTMP about System Runlevel Changes.
Apr 13 15:48:16 nsdc-trs80.kuntzilla.com systemd[1]: Startup finished in 1.221s.
Apr 13 15:48:17 nsdc-trs80.kuntzilla.com samba[24]: samba version 4.4.5 started.
Apr 13 15:48:17 nsdc-trs80.kuntzilla.com samba[24]: Copyright Andrew Tridgell and the Samba Team 1992-2016
Apr 13 15:48:18 nsdc-trs80.kuntzilla.com samba[24]: samba: using 'standard' process model
Apr 13 15:48:18 nsdc-trs80.kuntzilla.com samba[24]: Failed to bind to ipv6:fdab:d31d:931c:0:1858:b7ff:fe80:10cf:389 - NT_STATUS_ADDRESS_NOT_ASSOCIATED
Apr 13 15:48:18 nsdc-trs80.kuntzilla.com samba[24]: task_server_terminate: [cldapd failed to setup interfaces]
Apr 13 15:48:18 nsdc-trs80.kuntzilla.com samba[24]: Failed to bind to fdab:d31d:931c:0:1858:b7ff:fe80:10cf:88 UDP - NT_STATUS_ADDRESS_NOT_ASSOCIATED
Apr 13 15:48:18 nsdc-trs80.kuntzilla.com samba[24]: task_server_terminate: [kdc failed to setup interfaces]
Apr 13 15:48:18 nsdc-trs80.kuntzilla.com samba[24]: samba_terminate: cldapd failed to setup interfaces
Apr 13 15:48:18 nsdc-trs80.kuntzilla.com samba[24]: samba_terminate: kdc failed to setup interfaces
Apr 13 15:48:19 nsdc-trs80.kuntzilla.com winbindd[38]: [2017/04/13 15:48:19.039464, 0] ../source3/winbindd/winbindd_cache.c:3245(initialize_winbindd_cache)
Apr 13 15:48:19 nsdc-trs80.kuntzilla.com winbindd[38]: initialize_winbindd_cache: clearing cache and re-creating with version number 2
Apr 13 15:48:19 nsdc-trs80.kuntzilla.com winbindd[38]: [2017/04/13 15:48:19.604910, 0] ../lib/util/become_daemon.c:124(daemon_ready)
Apr 13 15:48:19 nsdc-trs80.kuntzilla.com winbindd[38]: STATUS=daemon 'winbindd' finished starting up and ready to serve connections
Apr 13 15:48:19 nsdc-trs80.kuntzilla.com smbd[28]: [2017/04/13 15:48:19.865263, 0] ../lib/util/become_daemon.c:124(daemon_ready)
Apr 13 15:48:19 nsdc-trs80.kuntzilla.com smbd[28]: STATUS=daemon 'smbd' finished starting up and ready to serve connections
Apr 13 15:48:20 nsdc-trs80.kuntzilla.com samba[24]: /usr/sbin/samba_dnsupdate: Traceback (most recent call last):
Apr 13 15:48:20 nsdc-trs80.kuntzilla.com samba[24]: /usr/sbin/samba_dnsupdate: File "/usr/sbin/samba_dnsupdate", line 631, in <module>
Apr 13 15:48:20 nsdc-trs80.kuntzilla.com samba[24]: /usr/sbin/samba_dnsupdate: get_credentials(lp)
Apr 13 15:48:20 nsdc-trs80.kuntzilla.com samba[24]: /usr/sbin/samba_dnsupdate: File "/usr/sbin/samba_dnsupdate", line 123, in get_credentials
Apr 13 15:48:20 nsdc-trs80.kuntzilla.com samba[24]: /usr/sbin/samba_dnsupdate: raise e
Apr 13 15:48:20 nsdc-trs80.kuntzilla.com samba[24]: /usr/sbin/samba_dnsupdate: RuntimeError: kinit for NSDC-TRS80$@KUNTZILLA.COM failed (Cannot contact any KDC for requested realm)
Apr 13 15:48:20 nsdc-trs80.kuntzilla.com samba[24]: /usr/sbin/samba_dnsupdate:
Apr 13 15:48:20 nsdc-trs80.kuntzilla.com samba[24]: ../source4/dsdb/dns/dns_update.c:295: Failed DNS update - NT_STATUS_ACCESS_DENIED
Apr 13 15:58:19 nsdc-trs80.kuntzilla.com samba[24]: /usr/sbin/samba_dnsupdate: Traceback (most recent call last):
Apr 13 15:58:19 nsdc-trs80.kuntzilla.com samba[24]: /usr/sbin/samba_dnsupdate: File "/usr/sbin/samba_dnsupdate", line 631, in <module>
Apr 13 15:58:19 nsdc-trs80.kuntzilla.com samba[24]: /usr/sbin/samba_dnsupdate: get_credentials(lp)
Apr 13 15:58:19 nsdc-trs80.kuntzilla.com samba[24]: /usr/sbin/samba_dnsupdate: File "/usr/sbin/samba_dnsupdate", line 123, in get_credentials
Apr 13 15:58:19 nsdc-trs80.kuntzilla.com samba[24]: /usr/sbin/samba_dnsupdate: raise e
I’m stumped at this point as to why it just stopped working. There appear to be some IP v6 errors listed, but I only use v4 on my network.