yonigo yonigo - 1 month ago 13
Linux Question

redirect QEMU window output to terminal running qemu

Im trying to debug the boot sequence of a linux kernel with qemu,
the command i'm running is:

qemu -serial stdio -kernel <path to kernel> -hda <path to rootfs> -append "root=/dev/sda terminal = ttyS0"


During boot all the kernel messages are printed to the QEMU window.
Only when the boot has finished i get my prompt back to the terminal i ran QEMU in.

Now i can start using the kernel terminal I'm running and seeing the output in the terminal and not in QEMU window.

How do i get all messages including the boot messages to my terminal and not to QEMU window (because i cant scroll up in that window..) ?

Answer
  1. remove -serial stdio parameter
  2. add -nographic parameter
  3. and change the kernel parameter terminal = ttyS0 to console=ttyS0. This should do the trick.

qemu -nographic -kernel ./bzImage -hda ./image.hda -append root=/dev/sda console=ttyS0

You may want to check the script I use for kernel development: https://github.com/arapov/wrap-qemukvm (it's not very "production", but you can find useful qemu cli parameters there)

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