[NTLUG:Discuss] console on headless server... no serial port

[Chris Cox]

On Thu, 2010-01-07 at 12:04 -0600, Eric Waguespack wrote:
> I have a small form factor server that I run headless, but I would
> like to be able to console into it during boot, it only has usb ports,
> is it possible (with usb / serial adapters) to console in via usb?
> 

yes.

It can be a chicken and egg thing though.

For example, if you want to do this AND reach the BIOS settting, then
the BIOS would have to support (for example) a serial terminal connect
via USB (again, just an example).  But this probably isn't what you
are wanting (plus it's probably not possible on your host without
adding some special hardware).

With regards to most things, if your initrd is loading the USB
modules, or it's built into your kernel (not a module) and you have
a proper USB to Serial adapter (again, I'm assuming one kind
of popular headless console) and that module is also built in or inside
of the initrd, then you should be able to pass console= on the boot
line to specify where the console resides.

One problem... USB is "dynamic" so the device name can float depending
on what is connected.  I'll assume you only have one USB to serial
device though...

I haven't actually tried what I'm describing above. Most of my headless
boxes have a serial port.

With regards to the "console=" parameters, you can read all about that
in the kernel-parameters.txt file and serial-console.txt files in the
kernel documentation for your distro.

You'll have to edit your /etc/inittab (or wherever things get started
from) and add something to run a respawning "getty" on the USB serial
line (e.g. I use agetty).

(below is an example for a serial situation, and not a USB serial)
S0:12345:respawn:/sbin/agetty -L 115200 ttyS0 vt102

Supposedly grub can do serial console support.  I have not had to try
this because usually my systems have a BIOS based serial redirect that 
will work clear up until the Linux kernel takes over (so I get to do
system BIOS clear through grub using that).

Anyway, things to look at (no guarantees on making this work).

There "might" be other options for a "console", but I'm not aware
of anything off the top of my head.  There are certainly hints of
functionality to be found in things like "linuxrc" (SUSE) where
they allow for headless installation over ssh, vnc, etc.  So...
other things might be possible (just so many issues in making
something like this work).