[yocto] Bitbake does not apply changes and sometimes it removes the kernel-source directory

[simo]

Hi all,

I am using a 'poky fido 13.0.1' Yocto distribution and I am experiencing
some problem after modifying the Linux kernel code and recompiling it.

Bitbake is not applying the changes and sometimes deletes the source
folder (but I have a backup, of course).

>From yocto environment shell, I execute:

~$ bitbake linux-gumstix -c compile -f

and then to create an image and having a kernel file compiled available:

~$ bitbake core-image-base

What is the best way to recompile an edited source with bitbake from
shell ? And why it removes the kernel-source directory ?

Thank you in advance for your help.

Regards,
Simon