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Re: hostname curiosity [SOLVED] ...but curioser and curioser



Steve wrote:
> ---- "Mikkel L. Ellertson" <mikkel infinity-ltd com> wrote: 
>> Steve wrote:
>>> Cool! Adding 
>>>
>>> DHCP_HOSTNAME=yes
>>>
>>> to /etc/sysconfig/network-scripts/ifcfg-eth0 seems to have done
>>> the trick. Now there is a longer pause during booting when it gets
>>> to the Setting up eth0...[OK] line so I'm guessing it is waiting a
>>> little longer to get an answer from the dhcp server.
>>> Btw, where are the docs for the ifcfg-eth0 file syntax? There is
>>> no man page for it.
>>>
>>> Thanks
>>> Steve
>>>
>> /usr/share/doc/initscripts-8.86/sysconfig.txt
> 
> Interesting! 
> First, I think the entry for PERSISTENT_DHCLIENT option may
> explain what was happenning:
> 
> "Without this option, or if it is 'no'/'0', and BOOTPROTO=dhcp, [and this was set]
>       dhclient is run for the interface in "one-shot" mode; if the 
>       dhcp server does not respond for a configurable timeout, then
>       dhclient exits and the interface is not brought up - 
>       the '-1' option is given to dhclient.
>       If PERSISTENT_DHCLIENT=yes, then dhclient will keep on trying
>       to contact the dhcp server when it does not respond - no '-1'
>       option is given to dhclient. Note: this disables the automatic
>       checking for the presence of a link before starting dhclient."
> 
> I didn't have PERSISTENT_DHCLIENT in the configuration file so it
> would seem that the server did not respond in time when the machine
> was cold booted which explains why the hostname was not set but this
> also says that the interface is not brought up and yet it was.
> 
I do not think this is the problem.

> The second thing is that there is no DHCP_HOSTNAME option listed
> in the /usr/share/doc/initscripts-8.76.4/sysconfig.txt and yet it
> DHCP_HOSTNAME="yes" seems to work evem though PERSISTENT_DHCLIENT is
> still not set.
> 
It should be set to the hostname you desire. I am surprised that it
is not in the file. It is processed by the ifup-eth script.

> The third thing is that something is creating a
/etc/dhclient-eth0.conf file at boot time that contains this line:
> 
> send host-name "yes"; # temporary RHL ifup addition
> 
I am not sure what is creating it - I will have to look into it.

> Obviously, my host name is not "yes" so this must be some
> special, undocumented use of send host-name that make the
> dhcp client get the hostname from the server.
> 
I think it is causing the DHCP server to send the client a hostname.
It is probably a "feature" of the server, rather then something with
the client.

Mikkel
-- 

  Do not meddle in the affairs of dragons,
for thou art crunchy and taste good with Ketchup!

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