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using hostname from dhcp

In our network we set host names for machines in the dhcp server.

When I use the live CD in our internal network, however, the host name
assigned to the host (or rather: MAC address) is overriden by "debian".
If I boot with 'nohosts' I merely get 'localhost.localdomain' , as this
is the default /etc/hostname file left there.

I figured that 'debian' is better than nothing. However I would still
prefer to get the hostname.

The hostname is set by the following in /sbin/dhclient-script:

set_hostname() {
    local current_hostname=$(hostname)
    if [ -z "$current_hostname" -o "$current_hostname" = "(none)" ]; then
        hostname "$new_host_name"

I figure that the real fix for that may be to conditionally unset
'current_hostname' in a enter hook (only if we got a new hostname).

But for now I use a simple exit hook:
$ cat config/chroot_local-includes/etc/dhcp3/dhclient-exit-hooks.d/hostname

# if we got a new lease with a hostname, set the hostname

if [ "$reason" = 'BOUND' ] && [ "$new_host_name" ]
        hostname "$new_host_name"

Results will naturally differ if you use a different dhcp client. I
recently tried udhcpc and it was actually functional :-)

Notes on testing this:

If you use qemu / kvm with its usernet, you can tell it to set the
hostname it its built-in dhcp server using something along the lines of:

  kvm -net user,hostname=ian -net nic binary.img

In our network we use dnsmasq. Setting a "static" hostname entry there
is straight-forward:


00:11:22:33:44:55:66 ian

/etc/hosts:	ian

               Tzafrir Cohen
icq#16849755              jabber:tzafrir.cohen@xorcom.com
+972-50-7952406           mailto:tzafrir.cohen@xorcom.com
http://www.xorcom.com  iax:guest@local.xorcom.com/tzafrir

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