make mrproper
make menuconfig
i didnot update anything with this.

make dep
make bzImage
make modules
make modules_install
mv arch/i386/boot/bzImage /boot/subbu
cd /boot/grub

i added new entry to grub.conf


title Red Hat Linux (2.4.20-8)
root (hd0.8)
kernel /boot/subbu ro root =LABEL=/ hdb=ide-scsi
initrd /boot/initrd-2.4.20-8.img


but it is giving kernel panic error init not found..


is there any wrong in updated grub.conf




grub.conf file contains this entry before compilation...

title Red Hat Linux (2.4.20-8)
root (hd0.8)
kernel /boot/vmlinuz-2.4.20-8 ro root =LABEL=/ hdb=ide-scsi
initrd /boot/initrd-2.4.20-8.img

Because you made a couple of fatal mistakes;

make menuconfig
i didnot update anything with this.

Without applying a working configuration or creating one here, you built a bad kernel, try again.

The last step should be: make install
not: mv arch/i386/boot/bzImage /boot/subbu

The /boot/grub/grub.conf file will be updated automatically and the files you forgot to copy to the /boot directory will be in place also.