How to understand 'make oldconfig'?

[Parmenides]

>> 2. When there is a .config in /usr/src/linux indeed, make do nothing
>> but generate a copy of .config, namely .config.old.
>
> I don't understand.....

Other 'make XXXconfig' such as:

               make config
               make menuconfig
               make xconfig
               make defconfig

do some modification to the .config more or less. If 'make oldconfig'
have not ask some questions, then the .config does not changed. So, I
think the 'make oldconfig' does nothing.  I wonder what 'make
oldconfig' does.


2011/8/26 Mulyadi Santosa <mulyadi.santosa at gmail.com>:
> hi....
>
> On Thu, Aug 25, 2011 at 23:32, Parmenides <mobile.parmenides at gmail.com> wrote:
>> Hi,
>>
>>    I have tried to understand 'make oldconfig' command while
>> configurating kernel. I do some experiments and get the following
>> ideas:
>>
>> 1. When there is no a .config in /usr/src/linux,
>>    (1)  If there is no a /boot/config-x.y.z, make will ask some
>> questions and then produce a .config.
>>    (2)  Otherwise, make will copy the /boot/config-x.y.z to
>> /usr/src/linux/.config.
>>
>> My question: According to the messages generated by make, I get that
>> both 'make defconfig' and 'make oldconfig' will gerenate .config based
>> on 'i386_defconfig'. Why does 'make oldconfig' ask some questions,
>> while 'make defconfig' does not?
>
> because "make defconfig" is simply generating a default pre configured
> config file (it's based on i386_defconfig as you said).
>
> make oldconfig asks something? quite likely because you tried to fetch
> that config into newer kernel version. Thus, it asks your decision on
> what to do on those new introduced options.
>
>> 2. When there is a .config in /usr/src/linux indeed, make do nothing
>> but generate a copy of .config, namely .config.old.
>
> I don't understand.....
>
>
> --
> regards,
>
> Mulyadi Santosa
> Freelance Linux trainer and consultant
>
> blog: the-hydra.blogspot.com
> training: mulyaditraining.blogspot.com
>