Update a newly-created '.config' file with some predefined values

[Roman Storozhenko]

On Tue, May 30, 2017 at 12:28:34PM +0300, Roman Storozhenko wrote:
> Hello everybody,
> 
> I have a host machine and I have a VM machine running CentOS 7 with 3.x. There is
> a kernel source tree on the host. I have made 'make menuconfig',
> populated all options that I want to have in my custom kernel and as a
> result got a '.config' file. Then I copied a centos-default distro config file from my VM's
> 'boot' catalog to my host's kernel source tree catalog. So now I have
> two files in my source tree: '.config' and '.config.old'. I am able to
> see difference between them using the following command:
> 
>     scripts/diffconfig .config.old .config | less
> 
> But is there anyway to update values in '.config' file with the
> apropriate values from '.config.old' file?
> I just want to make sure that all modules will be included in a
> new custom kernel.
> 
> Thanks in advance,
> Roman

I have found a solution. There is a script: 

scripts/kconfig/merge_config.sh

It allows to mix many configuration files in a base config. For example:

scripts/kconfig/merge_config.sh -m -r .config
~/kernel/conf_mixins/.config_deb

There are kernel options in .config_deb that include some debugging to the kernel
default .config.