dns update from dhcp server ok for windows clients, not ok for linux (dhclient) clients

Hi,


The subjects says it all (almost):

we have a linux dhcp server (dhcp-3.0pl1-26) happily distributing ip
adresses, and updating our dns server (on a separate linux server, running
bind bind-9.2.1-1.7x.2).

on our windows desktops, we have no problems: they request an ip adress,
obtain it, and via the dhcp server the dns gets updated.

however, i needed to configure a network interface of a linux machine via
dhcp, and although the ip adress is acquired and the network interface is
brought up, somehow the dns does not get updated.

we only allow dns updates from the dhcp server, and i am surprised why there
would be a difference between a linux machine using dhclient to request an
ip adress, and a windows machine.

the /var/log/messages shows no errors from either dns or bind, but a clue
could be that the DHCPREQUEST doesn't seem to send the machine's hostname,
whereas the windows client do seem to send it.


look at these log entries:

this is a windows machine

Aug 6 14:22:22 frontend dhcpd: DHCPREQUEST for 172.21.3.228 from
00:90:27:23:21:88 (atlantis) via eth0
Aug 6 14:22:22 frontend dhcpd: DHCPACK on 172.21.3.228 to 00:90:27:23:21:88
(atlantis) via eth0

and this is from the linux machine

Aug 6 14:35:46 frontend dhcpd: DHCPREQUEST for 172.21.3.250 (172.21.3.2)
from 00:0b:db:d5:5c:7e via eth0
Aug 6 14:35:46 frontend dhcpd: DHCPACK on 172.21.3.250 to 00:0b:db:d5:5c:7e
via eth0

as you can see, the hostname of the linux machine is not displayed after the
mac adress, whereas the windows machine does show it.


Any ideas on how to solve this annoying problem ?


thanks,


Tom.

 

You need to use the "-h" flag with hostname on the dhcpcd_eth0 line in
/etc/conf.d/net. Like this:

dhcpcd_eth0="-N -R -h mylinuxboxname.fully.qualified.com"

This has to be set on each linux machine requesting dhcp service. It
passes its name request along to dhcpd, which in tern passes it along to
bind.

-Jeff

 

So, send the hostname!

The man pages are not that good IMHO, and on my distro one of the
crucial ones is missing for some reason. I think dhclient.conf(5) and
dhcp-options(5) pages may have the syntax you need.

I think it's more straightforward with dhcpcd(8) if you have that. You
can put the hostname on the command line:
dhcpcd -h hostname [-options] interface

 

Please trim your excess quotes!

[but nothing to indicate what distribution this Linux client uses]

What is /etc/conf.d? Whilst deceptive coding is always possible, one
rarely sees it in Linux distributions' shell scripts. So one might
reason safely that a "dhcpcd_eth0" variable would apply to the use of
dhcpcd on eth0.

Do you know what distro Tom uses? It wasn't mentioned nor even hinted
AFAICT in his post. Do you know what dhclient is?

What if the client has no /etc/conf.d? What if the client wants a DHCP-
provided ntp.conf and/or resolv.conf?