Re: how can i see booting messages ??

["Mumia W.." <paduille.4060.mumia.w@earthlink.net>]

On 10/26/2006 07:15 AM, Miles Fidelman wrote:
> debian wrote:
> > Hello,
> >
> > I still have problems with my new installation.
> > There is some important information (i think) displayed just after grub
> > starts booting about the hdd, but i can't see what it is because it goes
> > 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 seen
> > 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.

Some of them can be logged by enabling boot logging: /etc/default/bootlogd

> 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:
> http://www.tldp.org/HOWTO/Text-Terminal-HOWTO-17.html
> http://www.tldp.org/HOWTO/Remote-Serial-Console-HOWTO/index.html
>
> 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 
> cable)
> - 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 connected
> - 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.
>
> Miles

Or you could prevent gdm from starting upon boot and press Shift-PageUp. 
Shift-PageUp won't work if gdm takes over, so gdm would have to be 
disabled for whatever runlevel you want to do this in.


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paduille.4060.mumia.w@earthlink.net