Arch Linux

etoixpi

Member

Registered: 2015-04-16

Posts: 8

How to print all kernel messages to a file in /boot or USB?

I am debugging an early boot problem. I have a luks encrypted root and swap that sometimes fails to resume from hibernate. 9/10 times it works perfectly, but when it fails it leaves me with a black screen and the CPU fan running at full speed. Further, I don't think the drive gets decrypted or the logging service resumes, because there are no entries beyond the hibernate in the journal.

I am looking for a quick and dirty way to force all kernel messages out onto an unencrypted partition like /boot or a usb drive during early boot. They don't need to be parsed or stored in a fancy way, I just need them for debugging this issue.

My hope is to find and fix this issue(if I can!) or to file a very detailed and useful bug with the kernel team.

Thanks!

mich41

Member

Registered: 2012-06-22

Posts: 796

Re: How to print all kernel messages to a file in /boot or USB?

You can run

pm-hibernate ; something

and then something will be executed pretty much as soon as the kernel resumes from hibernation and unfreezes userspace processes.

The problem is that your system probably doesn't manage to reach this point. You can verify this with something like pm-hibernate;beep for example.

Try serial port console (if available) or netconsole.