how do i compile the kernal.

First, its kernel, not kernal.
Your not the first to ask this, I would have to suggest searching here and maybe reading the kernel howto at www.tldp.org.

"kernel compile recompile" search here: http://www.linuxquestions.org/questi...der=descending

The kernel howto at tldp.org:
http://www.ibiblio.org/pub/Linux/doc...nel-HOWTO.html

Some tips :

Your scenario might be different but there should be something useful here - Using 2.4.22, Red Hat 9 and LILO as an example.

Download the source
extract source into /usr/src
If there's a symlink to an old source tree in /usr/src, delete it, then
create a symlink to new source directory with

ln -s /usr/src/linux-2.4.22 /usr/src/linux

cd into new source directory via symlink ie

cd /usr/src/linux

make xconfig
make dep
make clean
make bzImage
make modules
make modules_install

cp System.map /boot/System.map-2.4.22
cp arch/i386/boot/bzImage /boot/bzImage-2.4.22

Kedit /etc/lilo.conf

copy the previous Red Hat stanza to make a new one - change the image directive to

image=/boot/bzImage-2.4.22

change the label name to what you want

save

as root

/sbin/lilo

How long will this take, like hours .

depends on your system, i will be generous, and give it 45 mins at minimum...it depends what you choose to compile, and like i said, it also depends on your system...