Kerberos debugging, save yourself some time

Last week I had quite a lot of 'fun' debugging Kerberos mostly in an 'AD Trust - RedHat IDM' Environment. The problem was that user logins were denied even though kinit and id requests worked as expected and showed the correct results. So I ended up troubleshooting the usual suspects, DNS and time (NTP) and there it was ... the timezone was not set up correct on the Windows AD side.

Problem number two, kerberized NFS.
Kerberized NFS to a client after daylight savings time changed stopped working. I currently live in a country where daylight savings time is a thing. After daylight savings time changed (set back 1 hour), one client was not able to mount the NFS share with an "access denied by server" message. So naturally, I check the usual suspects, DNS and NTP and everything seems to work fine. The Time was correct and DNS SRV records were present.
The error was still the time though and here's why:

Checking the client with 'timedatectl' showed that 'RTC in local TZ' was set to 'true'.
This setting is responsible for setting the Timezone in the hardware clock used by the system and with an old setting you'll have time differences. Kerberos was showing expire dates of 01/01/1970.

To fix this, run:

 [archy@stealth-falcon ~]$ sudo timedatectl set-local-rtc 0  
 [archy@stealth-falcon ~]$ sudo reboot

After a reboot, everything works as expected again. Conclusion here:
Save yourself some time, check NTP ... when debugging Kerberos.

Feel free to comment and / or suggest a topic.

Comments

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