pstore looks very promising. I tried pstore with backup as efivars and it works.
Although efivars works, I would like to use the pstore with ramoops and I am currently having difficulty in choosing the correct ramoops.mem_address.
I enabled the related configs and using command line parameters as shown in the documentation https://www.kernel.org/doc/html/v4.14/admin-guide/ramoops.html
Ex usage is: `mem=128M ramoops.mem_address=0x8000000 ramoops.ecc=1`
0x8000000 is the start of the kernel code section according to `/proc/iomem`. So, I need to find a different location.
In /proc/iomem I can see a few sections of ram marked as "System RAM" and "Reserved"
I tried to use these addresses but using them causes weird behavior and the system is freezing while booting up.
So, how do I select a 128 MB space on my ram and dedicate it for ramoops?
On Tue, Jun 1, 2021 at 5:40 PM Fox Chen <foxhlchen@xxxxxxxxx> wrote:
On Tue, Jun 1, 2021 at 2:07 PM manty kuma <mantykuma@xxxxxxxxx> 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@xxxxxxxxx> 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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