Configure IP at boot

http://www.kernel.org/doc/Documentation/kernel-parameters.txt
http://www.kernel.org/doc/Documentation/filesystems/nfs/nfsroot.txt

CONFIG_IP_PNP
ip auto config


ip=::::::

This parameter tells the kernel how to configure IP addresses of devices
and also how to set up the IP routing table. It was originally called
`nfsaddrs', but now the boot-time IP configuration works independently of
NFS, so it was renamed to `ip' and the old name remained as an alias for
compatibility reasons.

If this parameter is missing from the kernel command line, all fields are
assumed to be empty, and the defaults mentioned below apply. In general
this means that the kernel tries to configure everything using
autoconfiguration.

The parameter can appear alone as the value to the `ip'
parameter (without all the ':' characters before). If the value is
"ip=off" or "ip=none", no autoconfiguration will take place, otherwise
autoconfiguration will take place. The most common way to use this
is "ip=dhcp".

IP address of the client.

Default: Determined using autoconfiguration.

IP address of the NFS server. If RARP is used to determine
the client address and this parameter is NOT empty only
replies from the specified server are accepted.

Only required for NFS root. That is autoconfiguration
will not be triggered if it is missing and NFS root is not
in operation.

Default: Determined using autoconfiguration.
The address of the autoconfiguration server is used.

IP address of a gateway if the server is on a different subnet.

Default: Determined using autoconfiguration.

Netmask for local network interface. If unspecified
the netmask is derived from the client IP address assuming
classful addressing.

Default: Determined using autoconfiguration.

Name of the client. May be supplied by autoconfiguration,
but its absence will not trigger autoconfiguration.
If specified and DHCP is used, the user provided hostname will
be carried in the DHCP request to hopefully update DNS record.

Default: Client IP address is used in ASCII notation.

Name of network device to use.

Default: If the host only has one device, it is used.
Otherwise the device is determined using
autoconfiguration. This is done by sending
autoconfiguration requests out of all devices,
and using the device that received the first reply.

Method to use for autoconfiguration. In the case of options
which specify multiple autoconfiguration protocols,
requests are sent using all protocols, and the first one
to reply is used.

Only autoconfiguration protocols that have been compiled
into the kernel will be used, regardless of the value of
this option.

off or none: don't use autoconfiguration
(do static IP assignment instead)
on or any: use any protocol available in the kernel
(default)
dhcp: use DHCP
bootp: use BOOTP
rarp: use RARP
both: use both BOOTP and RARP but not DHCP
(old option kept for backwards compatibility)

Default: any