答复: IP get via Etherboot and IP get dhcpcd

YhLu YhLu at tyan.com
Wed Feb 25 21:34:00 CET 2004


Eric,

When using nfsroot to put rootfs in NFS server, I need to set "root=/dev/nfs
nfsroot=.... ip=bootp" to use mkelfImage to produce one. Elf for boot.

Then If there is ip-mac pair in the dhcpd.conf. The kernel can not get the
IP address from the DHCP server.

The dhcp in busybox seems something simple dhcp....

I will try to use dhclient.

Regards

YH.

-----邮件原件-----
发件人: ebiederman at lnxi.com [mailto:ebiederman at lnxi.com] 
发送时间: 2004年2月25日 18:49
收件人: LinuxBIOS
抄送: YhLu
主题: Re: IP get via Etherboot and IP get dhcpcd

Peter Stuge <stuge-linuxbios at cdy.org> writes:

> On Wed, Feb 25, 2004 at 05:10:44PM -0800, YhLu wrote:
> > Eric,
> > 
> > I put the the dhcpcd in the initrd. After boot system with LinuxBIOS +
> > Etherboot + elf ( with the initrd). I found the IP got by Etherboot and
> > dhcpcd is different.
> > 
> > I may only used fixed option in dhcpd.conf to make it get the same addr?

If you specify the mac address and a fixed ip address you should always get
the same IP.

> One explanation would be that Etherboot uses BOOTP while dhcpcd uses DHCP.
> Try making Etherboot speak DHCP as well.
> 
> Otherwise maybe you can set up a fake dhcpcd-eth*.info file with the IP,
> but I doubt dhcpd will approve the request for that same address unless
> you use a really short lease time.

There are a couple of other possibilities.

dhcpcd is a broken client and can be fooled into thinking a reply to
another client is for itself as it does not verify the dhcp reply
it uses has the mac address it is requesting an ip address for.

dhclient works correctly and is strongly configurable.  I think
busybox also includes a working dhcp client.

Etherboot filters dhcp replies looking for a filename so it will
have something to boot from.  If you have 2 dhcp servers answering
you that could explain the difference.


packet sniffers like tcpdump and ethreal are your friends, as well
as log files in /var/log/

Eric



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