hostname and dhcp

JJB Barbish3 at
Thu Feb 12 11:21:05 PST 2004

If I understand you correctly, you are talking about your system
which is connected to the public internet, and you are using the
FBSD built in DHCP client to get an lease from your ISP. Now if you
are an commercial user with an officially registered domain name and
static ip address from your ISP,  Your ISP has you in their DHCP
server with your FQDN and it's being sent to your system when you
get an new lease. The FBSD built in DHCP client is not configured to
accept that info which will auto populate the hostname= environment
variable.  Install the DHCP package on you system and configure It's
client to accept that info.

If you are not an commercial user, then the host name the ISP uses
for you is meaningless to you. If you have officially registered
domain name then use that in your hostname=  statement, like this,
hostname="", then that FQDN will be what sendmail uses
for all the users on your LAN. Then use DHCP server to pass the
major FQDN to all LAN PC, and those systems will append to the front
their system names and tell your DHCP server their full name.

If you do not have LAN or officially registered domain name, then
all you need, is to meet the domain nameing convention, and you are all set go. IE:

As far as reverse lookup goes, that is only on officially registered
domain names,  either yours, which really happens at the registry
hosting your domain name, or at the ISP if your using their email

On your system the value you use in hostname=  should also be in the
/etc/hosts file like this

::1			localhost		localhost

Hope this helps


-----Original Message-----
From: owner-freebsd-questions at
[mailto:owner-freebsd-questions at]On Behalf Of Evan Dower
Sent: Thursday, February 12, 2004 1:15 PM
To: freebsd-questions-local at
Cc: freebsd-questions at
Subject: Re: hostname and dhcp

Hmm... That is what I expected it to do, but when I tried it, I
ended up
with an empty hostname. Of course, I don't remember now if I
commented out
that line or just set it to empty. Actually, looking at
/etc/defaults/rc.conf I see that if I comment it out in /etc/rc.conf
it gets
set to the empty string in the default, so it shouldn't matter.
Anyway, like
I said, I tried that and just ended up with an empty hostname.
Perhaps that
indicates something is wrong with my configuration...
Thanks very much for the help (any other ideas?),
Evan Dower
Undergraduate, Computer Science
University of Washington
Public key:
Key fingerprint = D321 FA24 4BDA F82D 53A9  5B27 7D15 5A4F 033F 887D

>From: Lowell Gilbert <freebsd-questions-local at>
>To: "Evan Dower" <evantd at>
>CC: freebsd-questions at
>Subject: Re: hostname and dhcp
>Date: 12 Feb 2004 13:04:38 -0500
>"Evan Dower" <evantd at> writes:
> > I've actually been running FreeBSD for quite a while now, but
> > never known exactly how to handle this. In rc.conf, one must
specify a
> > hostname. If you're using DHCP to set up your network though,
> > FQDN (fully qualified domain name) can change without notice. It
> > like a Good Idea to have your hostname be your FQDN, since some
> > will do a reverse lookup on your IP to verify that it matches
> > hostname you supplied. In particular I'm thinking of SMTP
> > here. (send-pr doesn't work for me because my mail gets
rejected.) So,
> > when you're autoconfiguring your network interfaces, what should
> > put in rc.conf's hostname variable? Is there something else I
can do
> > that would allow me to have something nicer looking, but still
send my
> > FQDN when asked?
>If you don't set your hostname in rc.conf, dhclient should change
>for you when it finds out what it is.
>Lowell Gilbert, embedded/networking software engineer, Boston area:
>               resume/CV at
>               username/password "public"

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