[linux-elitists] WiFi and DHCP

Karsten M. Self kmself@ix.netcom.com
Fri Oct 5 10:32:06 PDT 2001


on Fri, Oct 05, 2001 at 09:01:16AM -0700, Don Marti (dmarti@zgp.org) wrote:
> I'm setting up an IBM ThinkPad as a WiFi base station (I have
> obsolete ThinkPads like most people have O'Reilly books) and ran
> into an interesting interaction of the pcmcia subsystem and dhcpd.
> 
> The pcmcia init script runs before the dhcp one, but the WiFi
> card isn't initialized yet by the time dhcpd tries to start --
> so it doesn't.
> 
> The quick fix is to put a sleep 10 in the pcmcia startup script, but
> the structure of init scripts seems to assume that network interfaces
> will be up after the network-relate scripts run.  In the case of
> PCMCIA, this is not true.

I've been known to modify init scripts, sometimes extensively.  There's
a weakness to the SysV Init process that it specifies _order_, but not
_dependencies_.  To a certain extent it might be convenient to specify
chains of actions that are to occur in a certain order.

Example:  I run ntpd on my systems.  I like to set initial time with
ntpdate.  But ntpdate needs networking (which may rely on another box
coming up properly).  So I put a several-minutes timeout into the
ntpdate, running the process in background.  Which means that when the
clock runs out, ntpd has already claimed the port...

Better would be to set the delay, run ntpdate, and then launch ntpd on
successful completion.  Current inits make this at best a custom
modification.

Peace.

-- 
Karsten M. Self <kmself@ix.netcom.com>        http://kmself.home.netcom.com/
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