Error during regenerate keytabs

[#1]

I encountered the following error when trying to regenerate keytabs. I have recently upgraded from HDP 2.6 to HDP 3.0. I am using FreeIPA. The name of the host of the ambari server is not ambari_server -- I am not sure why it tries to create a new principal HTTP/ambari_server@REALM.

2018-10-09 17:17:00,700 - Failed to create principal, HTTP/ambari_server@ZXCOMPUTERS.COM - Failed to create principal for HTTP/ambari_server@ZXCOMPUTERS.COM
STDOUT: 
STDERR: ipa: ERROR: The host 'ambari_server' does not exist to add a service to.

2018-10-09 17:17:21,815 - Failed to create principal,  - Failed to create new principal - no principal specified

[#2]

@Luc Machiels

The HTTP Principal are using in this format:

 HTTP/_HOST@_REALM

So the "_HOST" is actually replaced with the FQDN of the host. So in your case are you sure that "ambari_server" is the FQDN of your ambari server host ? OR have you recently changed the FQDN of your ambari server host?

Can you please share the output of the following commands from Ambari Server host?

# hostname -f
# cat /etc/hosts

.

[#3]

Hi Jay, thank you for your reply. The ambari server host is merlin-0

[root@merlin-0 ~]# hostname -f
merlin-0.zxcomputers.com
[root@merlin-0 ~]# cat /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
192.168.17.10 merlin-0.zxcomputers.com merlin-0
192.168.17.11 merlin-1.zxcomputers.com merlin-1
...