Where does the linux kernel panic message go?

Question

I don't know if it's related to SO. I know that when I use the Linux kernel panic function, its job is to freeze my system, but it takes 1 argument, a message. Where can I actually see the message if my system is completely frozen and I force shutdown my PC by holding the power-off button?

main.c

#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h> // panic

MODULE_LICENSE("GPL");

static int __init initialization_function(void)
{
    panic("Module: my message!\n");
    return 0;
}

static void __exit cleanup_funcion(void)
{    
    printk(KERN_INFO "Module: Cleanup done, exiting.\n");
}

module_init(initialization_function);
module_exit(cleanup_funcion);

By the way, I don't know how can I see the actual oops message, where and how can I see it?

Answer 1

It goes to the kernel console, the same place where printk() message goes. There is a screenshot in Wikipedia article on kernel panic:

Usually, you will be able to see it if the kernel panic happens at boot time.

As for what happens if you have a running desktop system, unfortunately I don't remember. Either you won't see it, or X/Wayland server will crash and you will see the message it in the console.

Answer 2

As you have noticed yourself, this is pretty tricky since the system gets frozen. What you can do is to have a look in the system log after reboot. Exactly how that is done depends on the distribution. On a system with systemd you can use journalctl -xe.