[syslinux] Testing for ISO boot in init-premount

Ady ady-sf at hotmail.com
Tue Jun 23 04:05:07 PDT 2015


> Varugis Kurien via Syslinux <syslinux at zytor.com> writes:
> 
> > I have a scenario where I need to test for whether I have booted via a
> > syslinux ISO image in init-premount as opposed to (say) PXE boot. Is
> > there any variable that I can test for this?
> 
> I don't think you can do this without bootloader support.  And if you
> can configure your boot loaders, then you can freely vary your kernel
> command line or initrd contents, so this question does not arise...
> So I'm not sure what you're after.  Maybe check out the IPAPPEND (or
> SYSAPPEND) directive.
> -- 
> Regards,
> Feri.
 
If the evaluation (before launching the kernel / OS / ISO image / 
whatever) consists on whether you are using either:
_ MEMDISK, vs.
_ non-MEMDISK

then there is ifmemdsk.c32. It might - or might not - be useful for 
your needs.

>From the perspective of the user, there is a "family" of c32 modules 
acting as "conditionals":

_ ifmemdsk.c32
_ ifplop.c32
_ ifcpu(64).c32
_ whichsys.c32

with special attention to whichsys.c32.

The SYSAPPEND directive might be of some use to differentiate network 
booting from non-network booting, at least indirectly, because certain 
values should result in zero / null when not using network booting. 
Yet, I am not sure how such evaluation would be in use; either the 
appended boot options are relevant for network booting, or they are not 
(so, you would need to know the difference before actually booting the 
"whatever you are trying to boot").

Instead of asking whether there is something that would match the way / 
method you think your goal should be achieved, perhaps you might want 
to write what your actual goal is.

Regards,
Ady.
 
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