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2002 Jan 04 15:08

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[vox-tech] complete serial console success! (was: Re: minicom help)
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[vox-tech] complete serial console success! (was: Re: minicom help)



keywords: grub, bootloader, serial ports, console, headless server

On Thu, Jan 03, 2002 at 05:15:34PM -0800, Henry House wrote:
[...]
> I still can't get grub to display anything to the serial port, using the
> instructions from the info page, namely to add the following to the grub
> installation script:
> 
> 	serial --unit=0 --speed=9600
> 	terminal serial
> 
> I shall try fiddling with the grub setup.

Okay, I finally have it :-). Steps:

1. Connect server (headless box) to client (with monitor and keyboard) via a
   null-modem serial cable. If I can find the parts I plan to re-wire the
	link with cat5 cable instead, to make it easier to fit the cable into a
	raceway.

1. Linux and grub both use 9600 baud, 8n1, with NO flow control. Configure
   minicom on client appropriately.

2. The grub info document is misleading. You do not need to reinstall grub to
	enable serial IO, unless your grub binaries have been compiled without
	serial support (Debian's is fine out of the box). Just add the following
	lines to /boot/grub/menu.lst:

		serial --unit=0 --speed=9600
		terminal --timeout=0 serial

	and your bootloader will be useable in the serial terminal the next time
	it runs.

3. Compile a kernel with serial drivers and console on serial support enabled
	(not as modules). I also removed all the video drivers, mouse and
	keuyboard drivers, and the VGA virtual terminal driver, since I have no
	use for them. If you leave the video drivers in, you must append
	'console=ttyS0' to the kernel arguments. Otherwise the first serial port
	is used by default. This lets you see the kernel's messages as it loads.

4. Add a line to /etc/inittab to run a getty process on the serial port
   (otherwise after the kernel is up you will be unable to log in). Example:

		T0:23:respawn:/sbin/getty -L ttyS0 9600 vt100
	
	Run 'telinit q' to test.

5. Optional: add ttyS0 to /etc/securetty. This allows root to log in on this
   terminal.  Otherwise you must log in as a regular user and use su.

6. Reboot and pat yourself on the back if all went according to plan :-).

-- 
Henry House
The attached file is a digital signature. See <http://romana.hajhouse.org/pgp>
for information.  My OpenPGP key: <http://romana.hajhouse.org/hajhouse.asc>.

Attachment: pgp00007.pgp
Description: PGP signature



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