kernel space logging

[Anand Arumugam]

On Thu, Mar 24, 2011 at 5:47 PM, Greg Freemyer <greg.freemyer at gmail.com> wrote:
> On Tue, Mar 22, 2011 at 1:13 PM, Anand Arumugam <anand.arumug at gmail.com> wrote:
>> Hello all!
>>
>> I would like to know how logging is done while the kernel is booting
>> up. More importantly I am looking for those files in the kernel source
>> that handles the logging part. Also I would like to know what gets
>> logged after the kernel is up and running.
>>
>> Thanks for your time.
>>
>> cheers,
>> -anand.
>
> Are you talking about the logs you see when you run dmesg?
>
> You are aware the kernel maintains a ring buffer that all printk's go into.
>
> Then there are API's that let userspace track the buffer and put the
> messages into on disk logs.
>
> dmesg just dumps out the ring buffer queue.
>
> The userspace API to the ring buffer is syslog().
>
> So during bootup I _assume_ the kernel is just logging to the ring
> buffer, and then when the system is operational enough, userspace gets
> all the boot messages out of the kernel via syslog() and puts them to
> on disk log files.
>
> It's not too magic.
>
> Greg
>

I was looking for the logging framework used by the kernel developers.
Not just the dmesg logs.