On Wed, 2022-01-26 at 14:48 -0800, Samuel Sieb wrote:
I think I figured out what he's doing and I'm kind of
surprised that
it works at all. He's expecting the system to use its IP address to
lookup its hostname. That seems wrong. Maybe what is working is
that the installer does that lookup and sets the hostname during the
install. But that setting has become transient for some reason (which
I think I've noticed, but didn't investigate). The DCHP server is
the one that's supposed to be supplying the hostname.
I don't see why that's wrong, there were plenty of things that discover
their hostname by doing a reverse look-up of their IP. And he
demonstrated several releases that worked exactly that way.
The inverse of that was there were plenty of things that would foul up
if the reverse lookup of their IP didn't work, or came up with
different answers than expected.
I remember coming across this in the past when setting up HTTP servers,
mail servers, etc. Apache springs to mind, in particular, it would
work out its hostname via reverse IP lookups if you don't manually set
it in the Apache configuration (it doesn't find out its hostname from
the host's hostname).
* DHCP can accept a hostname from a client, but it doesn't have to.
* DHCP can give a hostname to a client, but it doesn't have to, and
the client doesn't have to accept it.
* A host can find out its hostname from its IP address. I recall
having to specify how many dots to count to separate hostname from
domain name (e.g. if you were fred.bargle.flargle.net.au, your
domain name could bargle.flargle.net.au or flargle.net.au, and
therefore there were two possibilities of what your hostname might
be).
A particular advantage of having the host and domain names being worked
out from polling your DNS server is that the details will be consistent
with what everything else thinks you are.
--
uname -rsvp
Linux 3.10.0-1160.53.1.el7.x86_64 #1 SMP Fri Jan 14 13:59:45 UTC 2022 x86_64
Boilerplate: All unexpected mail to my mailbox is automatically deleted.
I will only get to see the messages that are posted to the mailing list.