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RE: how can i see booting messages ??


Works fine for me now, but I was wondering...
Is there a way to use normal terminal (the monitor, keyboard of the
specific server) and also serial redirection at the same time ?
When my server restarts, I can see everything on the monitor but also in
my ZOC terminal session on my laptop, which is connected to the COM port
on that server.
It would be easy if you just connect your serial cable to a server and
have instant access.
The way it is configured now, I only get output on my zoc terminal
session and not anymore on the server monitor as soon as grub starts


-----Original Message-----
From: Miles Fidelman [mailto:mfidelman@meetinghouse.net]
Sent: donderdag 26 oktober 2006 14:16
To: debian-user@lists.debian.org
Subject: Re: how can i see booting messages ??

debian wrote:
> Hello,
> I still have problems with my new installation.
> There is some important information (i think) displayed just after
> starts booting about the hdd, but i can't see what it is because it
> to fast and it is too far up to go with CTRL-PageUP.
> So, is there i way that i can pause or stop the messages so that i
> what it is ?
This question seems to get asked at least once a month.

About the only thing you can do is use a terminal or terminal program
with a good capture buffer.  There are a whole bunch of startup messages

that only go to the terminal and don't get logged anywhere.

If you're setting up a server, you can set things up to use a serial
terminal as your console, and then plug in a PC or laptop with a
terminal emulator program that can capture all the traffic.  If you're
building on a desktop PC, it might be a bit harder.

There are some references floating around for how to use a serial
terminal as a console, maybe start with:

I did this recently when building a couple of rackmount servers and it
was pretty helpful to capture the traffic.

Looking back at my (somewhat sketchy) notes, the basic steps involved:

1. connect both a regular terminal and a serial terminal

Note: Depending on what you're using, this may be the most difficult
part.  In my case, I was using a PowerBook, and had to pull together the

right combination of:
- USB-to-RS232 adapter (it's not just a cable, there are some level
changes going on so these beasts actually have a chip embedded in the
- RS232-to-RS232 adapter(s) for gender (male/female) and type (DCE/DTE)
I can't remember what I did here anymore, I just keep the properly
configured cable in my laptop case.
- terminal program: these are surprisingly hard to come by these days -
it's not that often one has to plug a dumb tty into a modem anymore - I
ended up digging up a copy of Zterm (Mac)
- configuring the terminal program (remember word length, parity, stop
bits, port speed and such?)

2. finding the right BIOS settings to:
- use the serial port (COM2 in my case) if a serial terminal is
- my server also has an option to use both the serial port and the
normal display

3. setting grub to use a serial terminal - somewhere in the grub config
(or maybe it was typed to grub - as I said, sketchy notes

serial --unit=0 --speed=9600 --word=8 --parity=no stop=1
terminal --timeout=10 serial console

I believe these two commands first set up the serial port, then tell
grub to use it for the terminal unless it times out in which case it
uses the regular terminal.

4. telling grub to start the kernal using the serial console - in my
case the boot command is:

kernel kernel /vmlinuz-2.6.8-3-686 root=/dev/mapper/rootvolume-rootlv ro

console=tty0 console=ttyS1,115200n8

5. going through the startup routine using only command line prompts

Hopes this helps.


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