we followed below procedure and not found kernel configuration in /boot

#rpmdev-setuptree
#rpm -ivh kernel-2.6.32.21-168.fc12.src.rpm
#cd /root/rpmbuild/SPECS
#rpmbuild -bp --target=$(uname -m) kernel.spec
#cd /root/rpmbuild/BUILD/kernel-2.6.32.fc12/linux-2.6.32.i686

#cp configs/kernel-2.6.32.21-i686.config .config
#make oldconfig
#make menuconfig
one window appear and select "Exit" and press "Enter"
#make -j4
#make modules
#make modules_install
#make install
#cd /lib/modules/2.6.32.21/build/
#make oldconfig
#init 6
boot with kernel-2.6.32.21


now in /boot directory not found kernel configuration file "config-2.6.32.21" but found vmlinuz, initrd and system.map files

how do create kernel configuration file in /boot

It's been quite a while since I compiled my own kernel, but cant you just copy your configs/kernel-2.6.32.21-i686.config file to /boot? If it's already there, perhaps it need to be named something like config-2.6.32.21-i686 (the config filename should look like the kernel filename with the word "config" substituted for the word "kernel")

after make install cannot generated config file in /boot directory but vmlinz, initrd, system.map generated

we missed any step cannot generated config file in /boot directory

You used a config file to generate your kernel. Take that file, wherever it is located and whatever its name, and copy it to /boot/config-2.6.32.21-i686

thanks