Kernel-level IP autoconfiguration and nodename

Kernel-level IP autoconfiguration and nodename

[Felipe Alfaro Solana]

Hi there!

I'm trying to deploy several diskless workstations using Ubuntu
Dapper. I've followed the steps highlighted in the Wiki
https://wiki.ubuntu.com/DisklessUbuntuHowto (plus some additional
modifications to get it working fine).

However, I'm unable to get the client machine get its hostname from
the DHCP server. What is really strange is that the kernel itself is
able to autoconfigure itself using DHCP, and I can see during boot
that a hostname is assigned to the client, as shown before:

IP-Config: eth0 complete (from 10.0.0.2):
 address: 10.0.0.10        broadcast: 10.255.255.255   netmask: 255.0.0.0
 gateway: 10.0.0.2         dns0     : 10.0.0.2         dns1   : 0.0.0.0
 host   : client1
 domain : lan
 rootserver: 10.0.0.2 rootpath:

However, both "uname -n" and hostname return "(none)". I have tried
hacking the initram, but I have been unable to guess why, although the
kernel is receiving a hostname via DHCP, hostname ends up being
"(none)".

I've been reading net/ipv4/ipconfig.c and seems like
system_utsname.nodename is being set to the host name received via
DHCP, but I can't guess why /proc/sys/kernel/hostname keeps returning
"(none)".

Any ideas?

Thank you very much.

Re: Kernel-level IP autoconfiguration and nodename

[Jan Engelhardt]

>
> However, I'm unable to get the client machine get its hostname from
> the DHCP server. What is really strange is that the kernel itself is
> able to autoconfigure itself using DHCP, and I can see during boot

I think that's obsolete since you can do it from initrd/initramfs for a 
looong time.
BTW, if so, why has not this been removed yet?

> that a hostname is assigned to the client, as shown before:
>
> IP-Config: eth0 complete (from 10.0.0.2):
> address: 10.0.0.10        broadcast: 10.255.255.255   netmask: 255.0.0.0
> gateway: 10.0.0.2         dns0     : 10.0.0.2         dns1   : 0.0.0.0
> host   : client1
> domain : lan
> rootserver: 10.0.0.2 rootpath:
>
> However, both "uname -n" and hostname return "(none)". I have tried

It is only a very simple dhcp client that only requests the lease 
once in a boot lifetime, even if the server will drop the lease when 
it expired.
Well, it does not explain your problem below, but IMO it's not worth 
looking into any further.

> hacking the initram, but I have been unable to guess why, although the
> kernel is receiving a hostname via DHCP, hostname ends up being
> "(none)".
>
> I've been reading net/ipv4/ipconfig.c and seems like
> system_utsname.nodename is being set to the host name received via
> DHCP, but I can't guess why /proc/sys/kernel/hostname keeps returning
> "(none)".
>
> Any ideas?
>
> Thank you very much.
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Jan Engelhardt
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