[yocto] Magic kernel config option.

[Brian Smucker]

Hi,

I'm a yocto mostly-newbie, trying to find my way.  I have a custom layer 
that I am using to build a kernel. The layer right now consists of a few 
kernel patches and a defconfig and is based on the standard kernel 
otherwise.

When I do a diff on my defconfig and the bitbake generated .config, they 
are quite similar, but the CONFIG_UNION_FS=y line magically shows up.  
I'm wondering where it comes from and how to disable it.

I can do a bitbake -c menuconfig virtual/kernel and eliminate that 
option giving me the kernel I want, but those changes are gone after a 
bitbake -c cleansstate ...

Could someone give me some help about where to go from here?

Thanks,
Brian