way to "duplicate" console contents to a file?

way to "duplicate" console contents to a file?

[Linda Walsh]

Is there a way to have my console messages duplicated and saved in a file?

I know about sending messages to "console" in [n]syslogd, but I'm
looking for the ability to essentially see a _copy_ of what is on the
screen.  There are messages that pop out on the console that I'd like to
view remotely, *and*, I would like to be able to review the startup
messages after the kernel has booted and while it is going through the
RC scripts.  Occasionally (often) I have some rc script that caused some
unexpected or weird output on boot that only "spews" its output onto the
console.  Even the running of the "rc" scripts -- that output seems to
be limited to the console.

Even for info that goes to the console, I'm only partly lucky in being
able to scroll back -- sometimes can't scroll back enough, or something
on occasion mungs the part of the scrollback buffer I want to view.

It know "dmesg" and boot.[o]msg show the kernel's startup messages, but 
maybe
it's when it stop's recording to klog and switches over to syslog that info
written to the console is no longer recorded.

I'd "sorta" like a "console" file like is in boot.msg for the kernel
boot -- something that is appended to for each session, the
re-initialized.  But startup scripts and sometimes drivers and such,
_appear_ to write messages to either /dev/console, /dev/tty, or
stderr/out with it mapped to the console.

I'd prefer not to disturb the way messages are displayed on the console
so when I am in front of the computer it will appear "normal" -- but
want the ability to display those messages when logged in remotely (more
normal case).

Ideas? Clue sticks? :-)
Thanks,
Linda

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Re: way to "duplicate" console contents to a file?

[Eric Bambach]

On Sunday 04 March 2007 18:02, Linda Walsh wrote:
> Is there a way to have my console messages duplicated and saved in a file?

Have you looked into using the serial console and some sort of secondary 
server to capture its output? It could be easily logged and stored. Serial 
consoles are started very early in the boot process so you would get almost 
all kernel message just after the kernel is invoked. Its a popular kernel 
hacker debugging method.

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-- 
Thanks,

Eric
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Re: way to "duplicate" console contents to a file?

[Linda Walsh]

Eric Bambach wrote:
> On Sunday 04 March 2007 18:02, Linda Walsh wrote:
>   
>> Is there a way to have my console messages duplicated and saved in a file?
>>     
> Have you looked into using the serial console and some sort of secondary 
> server to capture its output? It could be easily logged and stored. Serial 
> consoles are started very early in the boot process so you would get almost 
> all kernel message just after the kernel is invoked. Its a popular kernel 
> hacker debugging method.
>   
----
May end up using that method -- it's not idea though because it's
an "either/or" solution vs. a "co-solution".  Don't need the input
redirected, so much as just a log of output.

I wonder if something like klogd would be practical.  Something that stays
active and sweeps the display buffer of the console periodically and dumps
contents to file -- something like an "auditd" for the console (in the
respect that auditd takes messages from kernel and dumps to file).

Maybe would work best if console buff was kept in memory (kernel option
to use memory to allow as scroll-back).  Even so, I suppose it should be
possible to read out of video memory as well as writing into it (?)...

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Re: way to "duplicate" console contents to a file?

[Rajat Jain]

On 3/6/07, Linda Walsh <lkml@tlinx.org> wrote:
> Eric Bambach wrote:
> > On Sunday 04 March 2007 18:02, Linda Walsh wrote:
> >
> >> Is there a way to have my console messages duplicated and saved in a file?
> >>
> > Have you looked into using the serial console and some sort of secondary
> > server to capture its output? It could be easily logged and stored. Serial
> > consoles are started very early in the boot process so you would get almost
> > all kernel message just after the kernel is invoked. Its a popular kernel
> > hacker debugging method.
> >
> ----
> May end up using that method -- it's not idea though because it's
> an "either/or" solution vs. a "co-solution".  Don't need the input
> redirected, so much as just a log of output.

I think it is possible to specify multiple console= command line
arguments and the console output will be available on all. Somebody
please CMIIW.

Thanks,

Rajat

>
> I wonder if something like klogd would be practical.  Something that stays
> active and sweeps the display buffer of the console periodically and dumps
> contents to file -- something like an "auditd" for the console (in the
> respect that auditd takes messages from kernel and dumps to file).
>
> Maybe would work best if console buff was kept in memory (kernel option
> to use memory to allow as scroll-back).  Even so, I suppose it should be
> possible to read out of video memory as well as writing into it (?)...
>
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> To unsubscribe from this list: send the line "unsubscribe linux-newbie" in
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>
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