[Date Prev][Date Next] [Thread Prev][Thread Next] [Date Index] [Thread Index]

Re: how can i see booting messages ??

On 10/26/2006 07:15 AM, Miles Fidelman wrote:
debian wrote:

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:

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.


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.


Reply to: