1. Error kinit

root@krb:/home/user# kinit
kinit: Client not found in Kerberos database while getting initial credentials

solution :
we need to write user after kinit
example
root@krb:/home/user# kinit root/admin
Password for root/admin@EXAMPLE.COM :

2. Error krb5-rsh Client
root@krb:/home/user# krb5-rsh -x -PN krb.example.com
error getting credentials: Server not found in Kerberos database

solution :
we need to add princ “host” that is associated with krb services

users and the services must have an appropriate principal entry in the Kerberos database. While users are in form of NAME/ROLE, services are in form SERVICE-NAME/HOSTNAME. So we need to add a principal for service “host” (common name for all shell services), on host where the service is provided — krb.example.com.

sudo kadmin.local
Authenticating as principal root/admin@EXAMPLE.COM with password.

kadmin.local: addprinc -randkey host/krb.example.com

WARNING: no policy specified for host/monarch.spinlock.hr@SPINLOCK.HR; defaulting to no policy
Principal “host/krb.example.com@EXAMPLE.COM” created.

kadmin.local: ktadd -k /etc/krb5.keytab -norandkey host/krb.example.com

kadmin.local: quit

kinit root/admin

source : http://techpubs.spinlocksolutions.com/dklar/kerberos.html#krb-adduser-priv