Re: How does a linux dhcp client know it's name?

[Alan Chandler <alan@chandlerfamily.org.uk>]

On Monday 11 October 2004 14:59, Icebiker wrote:

>
> /etc/hostname said "flipper". I tried pasting the local domain name on (my
> DLink router has a field for local domain name), but that didn't seem to do
> anything.
>
> I can't figure out how:
>
> - the resolver gets the host name from /etc/hostname, if that's what's
> supposed to happen.

I "think" that

/etc/init.d/hostname.sh calls "hostname" to set the name from /etc/hostname  

the domain name comes from either /etc/hosts or from bind according to the 
setting in /etc/host.conf

This gives the order (although /etc/nsswitch.conf comes in somewhere too)

 If dns then looks in /etc/resolv.conf to find out where the dns is.  If file, 
it looks up /etc/hosts

dhcp3-client sets the info in /etc/resolv.conf.

You can cause a dhcp request to recognise the MAC address of the ethernet card 
and to use that to always issue the same ip address to your box. 

[NOT for your DLINK router - see why below]  In fact - better than that - the 
dhcp server can look up which ip address it wants to give you by looking up 
the name on a dns server.


> - the router gets the hostname from the box (it can get the hostname for
> all my Windows boxes). Does the dhcp request pass the name to the router,
> or does the router query for the name from the computer.

I can't image how it does this other than potentially using NETBUI


>
> Does anybody know what package contains the resolv+ man page? Is it still
> called resolv+

man hostname
man resolv.conf
man host.conf

are all useful

>
> I suppose I could set up static IP addresses, but that seems like giving
> up.

This is the way I do it

I have my own dhcp server and nameserver running on a linux box.  This is 
master for the rest of the network.  Its own ip address is static 
(/etc/network/interfaces). 192.168.0.10 is the DLINK router and 192.168.0.20 
is this linux box.  I use both as nameservers

The /etc/dhcp3/dhcpd.conf 

shared-network home-net {
  option domain-name "home";
  option domain-name-servers 192.168.0.20, 192.168.0.10;

  option subnet-mask 255.255.255.0;
  default-lease-time 21600;
  max-lease-time 86400;
  authoritative;
  subnet 192.168.0.0 netmask 255.255.255.0 {
    range 192.168.0.40 192.168.0.59;
    option routers 192.168.0.10;
  }

#  The following are hosts which require a fixed ip-address (for instance
#  so that NAT can direct things to them)
#

  host roo {
    hardware ethernet 00:50:da:ec:83:9a;
    fixed-address roo.home;
  }
  host rabbit {
    hardware ethernet 00:06:5b:b7:9c:35;
    fixed-address rabbit.home;
  }
  host piglet {
    hardware ethernet 00:0b:cd:a9:f2:62;
    hardware ethernet 00:06:25:2a:fa:25;
    fixed-address piglet.home;
  }
  host eeyore {
    hardware ethernet 00:0b:cd:32:77:75;
    hardware ethernet 00:20:e0:5e:18:67;
    fixed-address eeyore.home;
  }
  host kanger {
    hardware ethernet 00:50:DA:CF:A5:06;
    fixed-address kanger.home;
  }
  host pooh {
    hardware ethernet 00:30:1B:11:32:11;
    fixed-address pooh.home;
  }
  host small {
    hardware ethernet 00:06:25:57:19:5D;
    fixed-address small.home;
  }
  host owl  {
    hardware ethernet 00:09:5b:24:f1:12;
    fixed-address owl.home;
  }
}

subnet 82.43.0.0 netmask 255.255.0.0 {
  not authoritative;
}


-- 
Alan Chandler
alan@chandlerfamily.org.uk
First they ignore you, then they laugh at you,
 then they fight you, then you win. --Gandhi