append domain-name in /etc/dhcp/dhclient.conf has extra '.' in appended domainname

[gwolski]

Parallelcluster 3.11.1. Rocky 8.10.

While debugging another issue, I noticed that the entry you add to /etc/dhcp/dhclient.conf has a '.' at the end of the cluster domainname. Assuming my cluster is called rhel8c, here is what I see in /etc/dhcp/dhclient.conf:

DHCP Client Configuration file.

see /usr/share/doc/dhclient/dhclient.conf.example

see dhclient.conf(5) man page

Send client identifier as "hardware-type.link-layer address" (e.g. "1.c2.23.7d.c3.52.2c")

Required in environments where a bridge might be clobbering the forwarded

packet's MAC address (common in Wifi, Docsis, or ADSL bridging scenarios)

see dhcp-options(5) man page for 'dhcp-client-identifier'

see dhcp-eval(5) man page for 'hardware'

send dhcp-client-identifier = hardware;
append domain-name " rhel8c.pcluster.";

Note the extra period at the end of rhel8c.pcluster? I can't find anything in the documentation that says this is required.
I removed the period and sent a SIGHUP to Network manager to recreate the /etc/resolv.conf and the /etc/resolv.conf looks like it did before.

I'm no NetworkingManager expert and while things seem to work with the period (and even w/o) - it just seems wrong.

BTW, I would think it would be better to use "prepend" than append as most lookups are going to be hosts in the cluster, so it should try that domainname first?

[hgreebe]

The trailing dot serves to terminate the domain name, making it a fully qualified domain name. This signals that is should not be appended with any additional domain suffixes.

We use "append" because all the cluster domains in route53 end with "cluster_name.pcluster"

[gwolski]

Hi @hgreebe
Not sure I agree with you on either point. But

I ran a test case for the first situation and the '.' is stripped out when it is put in the /etc/resolv.conf.

As for your "append" description - that is wrong. Or maybe I'm misunderstanding you. I'm suggesting you should use 'prepend' instead of 'append' of the "cluster_name.pcluster" as putting it first on the search line will save at least one lookup. It's a nit. This is what prepend will do. Your present use of "append" puts it at the end of the search line in the /etc/resolv.conf so the hostname is first checked against other domains (which of course will all fail, hence more lookups).