Pausing kernel boot messages

Pausing kernel boot messages

[Esteban Fernandez]

How do you pause the kernel boot messages ?

^S, Pause and Scroll lock do nothing and you can't Shift-Page-Up  after a
kernel panic.

Thanks.

Re: Pausing kernel boot messages

[Hans-Jürgen Koch]

Am Montag 27 August 2007 13:21 schrieb Esteban Fernandez:
> How do you pause the kernel boot messages ?
> 
> ^S, Pause and Scroll lock do nothing and you can't Shift-Page-Up  after a
> kernel panic.

These are functions of a shell (like bash), which you haven't got yet during
kernel boot. You can read the kernel boot messages _after_ your system's up
using dmesg etc.
If you can't do that, e.g. because your kernel always hangs during boot, you
could enable a serial console in your kernel and watch/log your kernel 
messages with a terminal program running on a different computer.

Hans

Re: Pausing kernel boot messages

[Andreas Schwab]

Hans-Jürgen Koch <hjk@linutronix.de> writes:

> Am Montag 27 August 2007 13:21 schrieb Esteban Fernandez:
>> How do you pause the kernel boot messages ?
>> 
>> ^S, Pause and Scroll lock do nothing and you can't Shift-Page-Up  after a
>> kernel panic.
>
> These are functions of a shell (like bash),

Definitely not.  The shell is not a console driver, it only uses it.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
PGP key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: Pausing kernel boot messages

[Zilvinas Valinskas]

Esteban,

Alternatively, read Documentation/networking/netconsole.txt. Might help
or might not. It depends when system is crashing.

On Mon, 2007-08-27 at 13:53 +0200, Hans-Jürgen Koch wrote:
> Am Montag 27 August 2007 13:21 schrieb Esteban Fernandez:
> > How do you pause the kernel boot messages ?
> > 
> > ^S, Pause and Scroll lock do nothing and you can't Shift-Page-Up  after a
> > kernel panic.
> 
> These are functions of a shell (like bash), which you haven't got yet during
> kernel boot. You can read the kernel boot messages _after_ your system's up
> using dmesg etc.
> If you can't do that, e.g. because your kernel always hangs during boot, you
> could enable a serial console in your kernel and watch/log your kernel 
> messages with a terminal program running on a different computer.
> 
> Hans
> 
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Re: Pausing kernel boot messages

[Hans-Jürgen Koch]

Am Montag 27 August 2007 13:58 schrieb Andreas Schwab:
> Hans-Jürgen Koch <hjk@linutronix.de> writes:
> 
> > Am Montag 27 August 2007 13:21 schrieb Esteban Fernandez:
> >> How do you pause the kernel boot messages ?
> >> 
> >> ^S, Pause and Scroll lock do nothing and you can't Shift-Page-Up  after a
> >> kernel panic.
> >
> > These are functions of a shell (like bash),
> 
> Definitely not.  The shell is not a console driver, it only uses it.

Right, I wasn't precise. But it's still possible that you don't have your
keyboard available during early parts of the boot process.

Hans

Re: Pausing kernel boot messages

[Jan Engelhardt]

On Aug 27 2007 14:13, Hans-Jürgen Koch wrote:
>> >> How do you pause the kernel boot messages ?
>> >> 
>> >> ^S, Pause and Scroll lock do nothing and you can't Shift-Page-Up  after a
>> >> kernel panic.
>> >
>> > These are functions of a shell (like bash),
>> 
>> Definitely not.  The shell is not a console driver, it only uses it.
>
>Right, I wasn't precise. But it's still possible that you don't have your
>keyboard available during early parts of the boot process.

Yes, but a common error is "could not mount root", which is way after the
keyboard has been initialized. *In fact*, you can start initramfs, have your
PgUp/PgDown keys available, and when you exit out of initramfs without a valid
root filesystem, you lose the keys again.


	Jan
-- 

Re: Pausing kernel boot messages

[Chuck Ebbert]

On 08/27/2007 07:21 AM, Esteban Fernandez wrote:
> How do you pause the kernel boot messages ?
> 
> ^S, Pause and Scroll lock do nothing and you can't Shift-Page-Up  after a
> kernel panic.
> 

You could try linux-2.6-debug-boot-delay.patch from Randy Dunlap,
included in the Fedora 7 kernel.