I would start by fixing the DHCP on the subdomain subnet. You will want to send 
the correct "sub.company.org" for the option 15.


Gregory Young

From: [email protected] <[email protected]> On 
Behalf Of Lee, David (LA Int,RAL,LSCI)
Sent: October 4, 2019 4:22 AM
To: [email protected]
Subject: RHEL7 kickstart: how is hostname determined?

All our hosts are registered in an Infoblox DHCP+DNS service as 
MAC+IP+hostname.  We have two one domains and one subdomain.

When we kickstart-install a new RHEL7 host on the main domain, it cleanly gets 
its intended hostname from Infoblox/DNS.  We can see this very early on by 
doing an Alt-F2 and querying the hostname.  All is well.

But on the subdomain it gets the name "localhost.localdomain" (which seems to 
be the "in the absence of anything else" default).

A wireshark trace of installations shows a DHCP request and ack.  On the main 
domain this is quickly followed by a DNS PTR query from the host, giving the 
host's IP address and successfully returning the host's hostname.  By contrast, 
on the subdomain, this query is never initiated.  (On both domains, there are 
subsequent successful DNS queries of other things as part of the ensuing 
installation, demonstrating that DNS activity is happening.)

What might be triggering the hosts on the two different domains to behave 
differently, that is, send or not send that DNS/PTR query?

Looking deeper into that preceding DHCP request/ACK:  The main domain, where 
all works well, is (for example) "company.org".  The subdomain (where this lack 
of hostname issue arises) is a subdomain, e.g. "sub.company.org".  One oddity I 
spotted, is that the DHCP/ACK returns the same "domain-name" option-15 
"company.org" for both.  I wonder if that is precipitating a subsequent 
problematical behaviour in that "sub.company.org" context?

Any thoughts?  Thanks.

-- David Lee



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