[Samba] Samba 4.4.2 as AD server: clients OK but server fails "wbinfo -K"

[Gerben Roest]

I have set up a samba 4.4.2 AD server, and it works fine for its Windows
and Linux clients. Only the server itself behaves peculiar:

Linux accounts show up as DOMAIN\username (in prompt and with whoami),
on all Linux clients the user accounts are normal (just their username),

and only on the server "wbinfo -K username" fails. On the clients it
works. The server complains about that:

22:59:54 root at sambaserver:samba# wbinfo --verbose -K john
Enter john's password:
plaintext kerberos password authentication for [john] failed (requesting
cctype: FILE)
wbcLogonUser(john): error code was NT_STATUS_CONNECTION_DISCONNECTED
(0xc000020c)
error message was: The transport connection is now disconnected.
Could not authenticate user [john] with Kerberos (ccache: FILE)

The error in /usr/local/samba-4-4/var/log.wb-DOMAIN is:

[2016/04/20 23:00:04.704273,  1]
../source3/librpc/crypto/gse_krb5.c:416(fill_mem_keytab_from_system_keytab)
  ../source3/librpc/crypto/gse_krb5.c:416: krb5_kt_start_seq_get failed
(No such file or directory)
[2016/04/20 23:00:04.704321,  0] ../lib/util/fault.c:78(fault_report)
  ===============================================================
[2016/04/20 23:00:04.704369,  0] ../lib/util/fault.c:79(fault_report)
  INTERNAL ERROR: Signal 11 in pid 8564 (4.4.2)
  Please read the Trouble-Shooting section of the Samba HOWTO
[2016/04/20 23:00:04.704427,  0] ../lib/util/fault.c:81(fault_report)
  ===============================================================
[2016/04/20 23:00:04.704476,  0] ../source3/lib/util.c:791(smb_panic_s3)
  PANIC (pid 8564): internal error


Any ideas?

thanks

Gerben