[systemd-devel] Right way to do kexec

Mirco Tischler mt-ml at gmx.de
Wed Mar 21 17:16:53 PDT 2012

Am 22. März 2012 00:33 schrieb Lennart Poettering <lennart at poettering.net>:
> On Wed, 21.03.12 12:24, Marti Raudsepp (marti at juffo.org) wrote:
>> Hi,
>> I've been trying to figure out how to use systemd's kexec functionality right.
>> When one runs "systemctl kexec", systemd simply shuts down and
>> executes 'kexec -e'. For this to work, a kexec-able kernel has to be
>> already loaded.
>> Now, when do I load this kernel? Loading at startup means that I'm
>> simply wasting the memory most of the time when I'm not rebooting.
> But I think this is the theory of how things are done. I remember some
> issues with requiring continious memory which might be hard to come by
> if the kernel is loaded only very late.
> Might be something to discuss with the kexec folks.
>> And if I upgrade the kernel, the old kernel sticks around in memory --
>> but the point of rebooting is usually to load the *new* kernel?
> presumably yes

Unless you want to use kexec on panic. In that case the kexec kernel
should be loaded at boot, doesn't it? But I don't know if this is
actually in use or more a debugging tool for kernel devs.

> Lennart


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