kinit failing when AD user joining using smaercard PIN on ubuntu 20.04

[Ken Hornstein]

>We are login to Ubuntu 20.04 device using smartcard PIN. We are able to
>login as AD user successfully.  We are using Windows 2019 AD Server.

So, I don't know what this means.  I suspect that Kerberos isn't working
correctly here and you'll falling back to something else.

>We tried kinit manually but it's throwing error. It asks for PIN but
>immediately asks for password without waiting for pin to be entered.

So ... there are a LOT of ways for PKINIT to go wrong (that's the protocol
you use when using a smartcard), especially when a PKCS#11 module is
involved, and some of the failure modes end up causing weird things
to happen (and many of them cause fallbacks to a password prompt).  But
I'm not sure why you're running "sudo kinit [...]"; shouldn't you just
run kinit without sudo?  I am wondering if sudo is causing the PIN
prompt and kinit is giving your the password prompt.

My suggestion is to run kinit again with the environment variable
KRB5_TRACE set to point to a debug file.  E.g:

env KRB5_TRACE=/tmp/kinit.log kinit [extra kinit options here]

That might point you to what is going wrong.

--Ken