[gentoo-user] Capture dmesg output on boot?

[gentoo-user] Capture dmesg output on boot?

[Dan Cowsill]

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Hello list,

I've been trying to get to the bottom of my recent troubles with my IDE
controller working with the 2.6.28 kernel.  Now, linux never boots
without a kernel panic, so dmesg never gets logged...  Is there any way
to have the kernel dump the boot log somewhere?  I'd settle for
scrolling up, really.

Thanks,
Dan


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Re: [gentoo-user] Capture dmesg output on boot?

[James Ausmus]

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On Mon, May 11, 2009 at 5:16 PM, Dan Cowsill <danthehat@gmail.com> wrote:

> Hello list,
>
> I've been trying to get to the bottom of my recent troubles with my IDE
> controller working with the 2.6.28 kernel.  Now, linux never boots
> without a kernel panic, so dmesg never gets logged...  Is there any way
> to have the kernel dump the boot log somewhere?  I'd settle for
> scrolling up, really.
>

If you have a serial port, you can enable serial console in the kernel
config, and boot with a "console=ttyS0" kernel parameter, to see all the
output on a serially attached (via null modem cable or adapter) computer...

-James

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Re: [gentoo-user] Capture dmesg output on boot?

[Dan Cowsill]

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James Ausmus wrote:
> If you have a serial port, you can enable serial console in the kernel
> config, and boot with a "console=ttyS0" kernel parameter, to see all
> the output on a serially attached (via null modem cable or adapter)
> computer...
>  
> -James
>
Hey, thanks for the advice.

Would that allow me to scroll the output?  Seeing the output isn't the
problem, its just that the relevant error messages scroll away too quickly.

Thanks,
D


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RE: [gentoo-user] Capture dmesg output on boot?

[Adam Carter]

> I've been trying to get to the bottom of my recent troubles
> with my IDE
> controller working with the 2.6.28 kernel.  Now, linux never boots
> without a kernel panic, so dmesg never gets logged...  Is
> there any way
> to have the kernel dump the boot log somewhere?  I'd settle for
> scrolling up, really.

Have you tried <shift>+<PgUp> ? I have no idea if it will work in that circumtance...

Remember that depending how you setup the kernel the IDE devices could be hdX or sdX.

Re: [gentoo-user] Capture dmesg output on boot?

[Dan Cowsill]

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Adam Carter wrote:
> Have you tried <shift>+<PgUp> ? I have no idea if it will work in that circumtance...
>
> Remember that depending how you setup the kernel the IDE devices could be hdX or sdX.
>
>   

Thanks,

Yes, I've tried shift+pgUp and it doesn't appear to work.  And yes, I've
verified that my root argument is the proper notation.

D


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Re: [gentoo-user] Capture dmesg output on boot?

[Valmor de Almeida]

Dan Cowsill wrote:
> Adam Carter wrote:
>> Have you tried <shift>+<PgUp> ? I have no idea if it will work in that circumtance...
>>
>> Remember that depending how you setup the kernel the IDE devices could be hdX or sdX.
>>
>>   
> 
> Thanks,
> 
> Yes, I've tried shift+pgUp and it doesn't appear to work.  And yes, I've
> verified that my root argument is the proper notation.
> 
> D
> 
I had similar problem in the past when the livecd would boot on hda but
once I booted into the new kernel I had to set fstab to sda.

As far as saving the messages during boot, there is a kernel parameter
that allows for scrolling the messages but only after the hd is mounted.
This is too late for checking kernel panic messages for example.

--
Valmor

[gentoo-user] Re: Capture dmesg output on boot?

[ABCD]

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Dan Cowsill wrote:
> Hello list,
> 
> I've been trying to get to the bottom of my recent troubles with my IDE
> controller working with the 2.6.28 kernel.  Now, linux never boots
> without a kernel panic, so dmesg never gets logged...  Is there any way
> to have the kernel dump the boot log somewhere?  I'd settle for
> scrolling up, really.
> 
> Thanks,
> Dan
> 

If it panics on attempting to mount the root file system, then you
probably would be able to use the S-PgUp if you give the "rootwait" or
"rootdelay=<#>", where "<#>" is a number of seconds.  "rootwait" would
tell the kernel to wait until it really thinks it can mount the root
filesystem before mounting it; "rootdelay=10" would tell the kernel to
wait 10 seconds before mounting.  Either way, you may be able to scroll
up during the delay (I don't remember if it initializes the keyboard
driver before or after the root filesystem, it's been a while since I've
had to debug that part of startup).

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Re: [gentoo-user] Capture dmesg output on boot?

[Daniel Iliev]

On Mon, 11 May 2009 20:16:55 -0400
Dan Cowsill <danthehat@gmail.com> wrote:

> Hello list,
> 
> I've been trying to get to the bottom of my recent troubles with my
> IDE controller working with the 2.6.28 kernel.  Now, linux never boots
> without a kernel panic, so dmesg never gets logged...  Is there any
> way to have the kernel dump the boot log somewhere?  I'd settle for
> scrolling up, really.
> 
> Thanks,
> Dan
> 


Add "panic=X" to your kernel parameters and after panic it will wait for
X seconds before rebooting.


-- 
Best regards,
Daniel

Re: [gentoo-user] Capture dmesg output on boot?

[Peter Humphrey]

On Tuesday 12 May 2009 01:28:17 Dan Cowsill wrote:

> Seeing the output isn't the problem, its just that the relevant error
> messages scroll away too quickly.

Have you tried CTRL-S to pause the output and CTRL-Q to resume?

-- 
Rgds
Peter

Re: [gentoo-user] Capture dmesg output on boot?

[Dale]

Peter Humphrey wrote:
> On Tuesday 12 May 2009 01:28:17 Dan Cowsill wrote:
>
>   
>> Seeing the output isn't the problem, its just that the relevant error
>> messages scroll away too quickly.
>>     
>
> Have you tried CTRL-S to pause the output and CTRL-Q to resume?
>
>   

Or maybe the scroll lock key?  That works on mine.

Dale

:-)  :-) 

Re: [gentoo-user] Capture dmesg output on boot?

[Dan Cowsill]

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Hello again list,

After having tried every suggested method of scrolling or pausing kernel
output and failing, I decided to mess about with the kernel config a
little more and eventually came out ahead.  I am happy to report no
kernel panics and I thank everyone for their contribution.

D


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Re: [gentoo-user] Capture dmesg output on boot?

[David Relson]

On Mon, 11 May 2009 17:20:10 -0700
James Ausmus wrote:

> On Mon, May 11, 2009 at 5:16 PM, Dan Cowsill <danthehat@gmail.com>
> wrote:
> 
> > Hello list,
> >
> > I've been trying to get to the bottom of my recent troubles with my
> > IDE controller working with the 2.6.28 kernel.  Now, linux never
> > boots without a kernel panic, so dmesg never gets logged...  Is
> > there any way to have the kernel dump the boot log somewhere?  I'd
> > settle for scrolling up, really.
> >
> 
> If you have a serial port, you can enable serial console in the kernel
> config, and boot with a "console=ttyS0" kernel parameter, to see all
> the output on a serially attached (via null modem cable or adapter)
> computer...
> 
> -James

An alternative to the serial port is your ethernet connection.  The
kernel can output to ethernet and you can capture the info using
netconsole.