kexec --real-mode

Eric W. Biederman ebiederm at
Wed Apr 23 10:00:57 EDT 2008

Bernhard Walle <bwalle at> writes:

> * Jamey Sharp [2008-04-22 16:44]:
>> On Tue, Apr 22, 2008 at 6:16 AM, Bernhard Walle <bwalle at> wrote:
>> > did anybody try the --real-mode option with current release? I tried
>> > it on two machines, and on one machine it just reboots, on the other
>> > machine it hangs.
>> I think you're experiencing a bug that I just proposed a patch for. :-)
>> You can confirm that: try adding the "--debug" option to your kexec
>> call. If that works correctly, then I think you'll find that the patch
>> in "[PATCH 2/9] Fix copy-paste bug: entry16 does not start at
>> entry16_debug" will solve your problem. That's archived here:
> No, I used --debug already.

If this used to work when booting older kernels on your hardware.
Jamey's patch 3/9 might help.

Otherwise if this is the first time you are trying it you may
simply have encountered the reason that --real-mode is not the default.
BIOS can get really strange after the kernel has been running.

When I had that the default I only had around a 50% success rate or
something like that.

You might try booting kexec_test and see where that puts you.


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