Missing panic logs in /var/log/kern.log

Fox Chen foxhlchen at gmail.com
Tue Jun 1 04:40:19 EDT 2021

On Tue, Jun 1, 2021 at 2:07 PM manty kuma <mantykuma at gmail.com> wrote:
> I am using debian , the logging system being used is rsyslogd.
> in /etc/rsyslog.d/default.conf we have rule as follows:
> ```
> kern.* /var/log/kern.log
> ```
> This rule I believe is the reason why all the kernel logs are being redirected to /var/log/kern.log.
> Also dmesg does not show anything. So, i am pretty sure that all the kernel logs are being handled solely by `rsyslogd`
> And this is just the default debian distribution without any customizations.
> Thank you for the 'pstore' clue. I will explore it further.
> On Tue, Jun 1, 2021 at 2:42 PM Greg KH <greg at kroah.com> wrote:
>> On Tue, Jun 01, 2021 at 02:33:50PM +0900, manty kuma wrote:
>> > I just triggered a panic, expecting that the logs will be visible in
>> > `/var/log/kern.log` after reboot, but there are no logs present there.
>> I have never heard of kernel logs being written to that location, what
>> tool do you have that does that and where is that documented?
>> > Considering I have no access to the serial port, how do I know what went
>> > wrong?
>> When the kernel panics, it usually can not write to the disk, so it's a
>> bit hard to save anything :)
>> That being said, there are ways the kernel can save the crash
>> information, look into the "pstore" interface and see if that will work
>> for your hardware platform (it requires hardware to store the
>> information across boots.)

Also, check kdump, I think it can help as well.

>> good luck!
>> greg k-h
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