Pausing kernel boot messages

Esteban Fernandez

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Aug 27, 2007, 7:30:15 AM8/27/07

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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.
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Hans-Jürgen Koch

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Aug 27, 2007, 8:00:12 AM8/27/07

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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

Andreas Schwab

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Aug 27, 2007, 8:00:12 AM8/27/07

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Hans-Jürgen Koch <h...@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, sch...@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."

Hans-Jürgen Koch

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Aug 27, 2007, 8:20:11 AM8/27/07

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Am Montag 27 August 2007 13:58 schrieb Andreas Schwab:
> Hans-Jürgen Koch <h...@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

Zilvinas Valinskas

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Aug 27, 2007, 8:20:13 AM8/27/07

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Esteban,

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

Jan Engelhardt

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Aug 30, 2007, 3:20:10 PM8/30/07

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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
--

Chuck Ebbert

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Aug 31, 2007, 1:00:15 PM8/31/07

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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.