AUTHOR: Richard A Downing FBCS <geek109@yahoo.co.uk>

DATE: 2003-09-29

LICENSE: GNU Free Documentation License Version 1.2

SYNOPSIS: Naming Network Interfaces.

DESCRIPTION:
This hint describes how to specify your own names for Network
Interface Cards instead of eth0, eth1, etc...

PREREQUISITES:
In principle the hint applies to all versions of LFS, and probably also
to all LINUX distributions.  However, the bootscript recommendations are
based on LFS-Bootscripts-1.11 (LFS-4.1).

HINT:

Introduction
============

When the Linux kernel boots, it assigns names (eth0 etc..) to
network devices in the order that it finds them.  This means that two
different versions of the kernel, say 2.4 and 2.6, might find the network
interfaces in a diffent order.  When this happens you might have to
swap all the cables to get your connections to work the way you want.
The proper way to do this is to name the interfaces with the nameif
command (part of the net-tools).

TAKE CARE: All the commands given in this hint need root priviledges.

MACTAB and NAMEIF
=================

The nameif command can be driven from the command line, if you want to
do that, then read it's man page.  Another way is to set up a
/etc/mactab file to relate the MAC addresses of the network cards to
the names you want.

Every NIC interface in the (known) universe has a unique MAC address
(Media Access Control address), which is usually expressed as a 12 digit
hexadecimal number, colon-dotted in pairs for readability. 

You will need to find the MAC addresses of each of your network cards.
The easiest way to find these (if you didn't make a note of the MAC
label when you installed the card) is to use ifconfig, each interface
that is configured will report its MAC address.  e.g:

$ /sbin/ifconfig
eth0      Link encap:Ethernet  HWaddr 00:60:97:52:9A:94  
          inet addr:192.168.1.3  Bcast:192.168.1.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:6043 errors:0 dropped:0 overruns:0 frame:0
          TX packets:6039 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100 
          RX bytes:1439604 (1.3 Mb)  TX bytes:509857 (497.9 Kb)
          Interrupt:10 Base address:0xc800 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:7218 errors:0 dropped:0 overruns:0 frame:0
          TX packets:7218 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:1085452 (1.0 Mb)  TX bytes:1085452 (1.0 Mb)

Take note of the HWaddr, this the NIC's MAC address.

Now you can decide what you would like the NIC to be called, and set
up your /etc/mactab, here's mine as an example:

# Begin /etc/mactab
# This file relates MAC addresses to interface names.
# We need this so that we can force the name we want
# even if the kernel finds the interfaces in the
# wrong order.

# eth0 under 2.4, eth1 under 2.6
beannet 00:60:97:52:9A:94

# eth1 under 2.4, eth0 under 2.6
sparenet 00:A0:C9:43:8F:77

# End /etc/mactab

If you run nameif (without parameters) now you will probably get an
error message, since nameif must be run when the interfaces are down.

$ nameif
cannot change name of eth0 to beannet: Device or resource busy

so, first take the interface down, then rename it:

$ ifconfig eth0 down
$ nameif
$ ifconfig eth0 up
$ ifconfig
beannet   Link encap:Ethernet  HWaddr 00:60:97:52:9A:94  
          inet addr:192.168.1.3  Bcast:192.168.1.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:6617 errors:0 dropped:0 overruns:0 frame:0
          TX packets:6596 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100 
          RX bytes:1748349 (1.6 Mb)  TX bytes:598513 (584.4 Kb)
          Interrupt:10 Base address:0xc800 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:9097 errors:0 dropped:0 overruns:0 frame:0
          TX packets:9097 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:1340480 (1.2 Mb)  TX bytes:1340480 (1.2 Mb)


LFS Bootscript Changes
======================

As we've seen, nameif needs to be run early in the boot cycle, before
the network interfaces are brought up.  This means adding it to
/etc/rc.d/init.d/network.

Edit the start of the file as follows:

#!/bin/bash
# Begin $rc_base/init.d/network - Network Control Script

# Based on ethnet script from LFS-3.1 and earlier.
# Rewritten by Gerard Beekmans  - gerard@linuxfromscratch.org

source /etc/sysconfig/rc
source $rc_functions
source /etc/sysconfig/network

case "$1" in
    start)
         if [ -e /etc/mactab ]
         then
         # if /etc/mactab exists then set up the named interfaces
             nameif
         fi
         for file in $(grep -il "ONBOOT=yes" $network_devices/ifconfig.*)
         do
......

This ensures that nameif is run with /etc/mactab, if that file exists.

Now go to /etc/sysconfig and change the name(s) of the interface(s) wherever
it(they) occur(s).  I made the following changes:

1) edit /etc/sysconfig/network to specify the renamed GATEWAY_IF.
2) rename /etc/network-devices/ifconfig.eth0 to ifconfig.yourname and
   edit it so that DEVICE=yourname.

If you use the Beyond Linux From Scratch instructions to use DHCP,
then you will need to substitute your new NIC names in the scripts and
filenames in the appropriate places.

ACKNOWLEDGEMENTS:
  * Kevin Fleming for pointing the nameif command out to me.

CHANGELOG:
[2003-09-29]
  * Initial hint.

