Touch based Dual Boot Menu

Werner Almesberger werner at
Fri Jan 9 01:13:40 CET 2009

Petr Vanek wrote:
> so each distro would have to supply zImage... or can one locate the
> build directory where our [fr owners :)] kernels come from, so one
> could get t zImage from there?

Hmm yes, that would be one option. Other possibilities include:

- add uImage support to kexec-tools

- teach Qi to read zImage. This would also get rid of the tools/mkimage
  dependency. Qi gets the following information from the header:

  - magic number,
  - image size (useful if we're booting from a raw device), and
  - a CRC of the compressed kernel

  A zImage has all this as well, except that the CRC is of the
  uncompressed kernel. So if Qi was to use zImages, there would be no
  easy way to detect and reject corrupt kernels.

  Kernels do get corrupted in real life, usually as a consequence of
  an interrupted file transfer. If loading the kernel from a file
  system, we would know the file size, so any mismatch there could be
  used as a "poor man's checksum".

  Andy, what do you think of this idea ?

I forgot to mention in this thread that, as long as it's one kernel
with multiple file systems, you don't actually need kexec. Instead,
you can just switch root file systems with pivot_root.

This is not only a little simpler but it also saves the time it would
take to bring up the second kernel.

- Werner

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