Question

I am trying to compile a newer Android kernel on my phone. The problem is it ends up in a boot loop without any means to access error messages. I can compile an older version of the kernel wich runs well on the phone, so I am able to add custom things to the kernel configuration if needed.

My goal is to boot up the phone with the old, working OS, then boot up the new kernel from the working OS and being able to get log messages during the new kernel’s boot.

If this is impossible, is there a way (for example to save messages to the SD card) to access kernel (error) log messages later (after booting up an other working OS).

Answer 1

I dont know if this will help you but I found a way to boot a Android kernel with console messages on screen. You need to boot your device in fastboot mode – this can be very diffrent for diffrent devices, here are some general info about fastboot: http://android-dls.com/wiki/index.php?title=Fastboot
For my device I can access boot loader by using adb and the command:

adb reboot bootloader

You will need to have fastboot binary on your pc. Then connect the phone to the pc in fastboot mode and write a following command:

fastboot boot [path/to/your/kernel]

Phone should try to boot a kernel and print some messages to the screen. You may need to tweak some parameter like command line args passed to the kernel (look at output of “fastboot help” ).