Linux installation: Second Ethernet interface ...

[mikebw at bilow.bilow.uu.ids.net (Mike Bilow)]

root wrote in a message to Mike Bilow:

 r> One  puzzle  is  that I've been using the control panel, and
 r> its cute little Network Configurator window looks like  it's
 r> doing  the  job. I've  several times created (and/or
 r> removed) the eth1 interfact, with an IP address starting
 r> with 10..., proto=none, atboot=yes,  and  I've pressed  the
 r> Activate button so that it says "active" in the "active"
 r> column.  And I've pressed the Save button.  No eth1 in 
 r> sight.   Both "ifconfig -a" and "netstat -i" show lo0 and
 r> eth0, but not eth1. 

You have me completely mystified.  I have no idea what the "control panel" is
-- at least not in Linux.  Usually, configuration of network hardware is done
through the command line.

 r> I've  also  tried several suggestions from the various
 r> HOWTOs and the mediaone  web  page,  especially  the  bit 
 r> about  adding  things  to /etc/lilo.conf, and none of them
 r> has worked.  During boot, it says:    ...  modprobe:  can't
 r> locate module eth1
 r> and sure enough, there's no eth1. Of course, I'd think that
 r> "eth1" is the name of an interface (i.e., a data structure
 r> in the kernel),  not a module (whatever that may mean here).
 r>  But what do I know? 

This is a little complicated.  In "/etc/modules.conf", you will find a mapping
of device names such as "eth0" and "eth1" to the appropriate network driver
module.  If you edit this file, you will need to run "depmod -a" to rebuild the
module dependency and other information, and then you will need to restart the
running kerneld instance by sending it a "-HUP" signal.  If you didn't follow
this, have a look through the Modules HOWTO.

By default, if there is no mapping, then kerneld will assume that the name of
the module is the same as the name of the device, which is why you are getting
the particular message you are getting.

 r> In any case, the terminology seems a bit confused.  What does 
 r> it mean to "activate" an interface?  Is this a synonym for 
 r> "create"?  If not, when does should interface get created?

Technically, interfaces are "attached."  You don't create hardware with
software.  The "ifconfig" command performs the attachment.  It does this by
making a request into the kernel, which transmits that request to kerneld to
try and load the driver module.  In turn, kerneld tries to run "modprobe",
which relies on the tables generated by "depmod", which originates back at
"/etc/modules.conf".

You can bypass this process with the "insmod" command which simply forces a
particular driver to be loaded, specified by filename.  Of course, this can
also crash your machine pretty quickly, but it is useful for testing.  Unless
you have a good reason for doing otherwise, "modprobe" should be used.

 r> And what sort of "module" is the boot code looking for and not 
 r> finding? It should already have the code for an Ethernet 
 r> interface, because it has eth0;  eth1  shouldn't need much more 
 r> than a new entry in a table.

No, for a number of reasons.  A simple example is that you could have put two
different types of Ethernet card into your machine, and they would each require
their own driver.  The machine is not going to know that unless you tell it,
and that is done here through "/etc/modules.conf".

 r> Anyhow, I thought I'd toss this out to some of the folks who've 
 r>  done it,  and  see  if there's something that should be 
 r> obvious, but which I'm just missing.

You have a simple problem.  Your automated installation just did not handle two
network cards, so you have to patch it up manually.
 
-- Mike