I have lilo.conf all setup for my new compiled kernel and I have run /sbin/lilo to install it. I am trying to get my new compiled kernel to work so after I create the bzImage and System.map and copy them to /boot; do I need to rerun lilo?

I keep reading statements like this on the web:

"You must re-run lilo even if entry 'mykernel' exists, everytime you create a new bzImage."

Question: What is /sbin/lilo doing such that I need to re-run it even though my lilo is already setup up correctly and I just copy in a new bzImage to /boot??

When you run lilo, it builds a new boot image for the computer to use when it starts. As long as the kernel you replace has the exact same name, you should be able to simply overwrite the file.

Unlike Grub, lilo needs to be rebuilt after each modification to the configuration or filenames, but not to data within the files.

With grub, instead of rebuilding the image everytime, you build the boot loader and tell it to read a file for configuration. From that point on, you simply edit the file with a text editor.

LILO needs to know the cyl/head/sector address of the kernel and initrd (if used) on the drive. This can change when you generate a new image. The reason it needs to know is because it does its setup at LILO time, not at boot time. It doesn't use ext2/reiser/whathaveyou when booting.

Conversely, GRUB accesses the file system through the ext2/reiser/whathaveyou at boot time, so as long as he knows the path he can find your new kernel, etc. This means that GRUB has to support your filesystem or he can't boot your system directly.

Both of these methods have their plusses and minuses. I personally prefer LILO and rerunning it is so trivial it doesn't bother me.

If the new image gets saved at a different c/h/s LILO won't be able to boot it. The name is really not the issue, it's the location on the drive.

When the computer boots up it doesn't know which filing system or operating system is in use. So there are no directories or filenames at this time only a disk with sectors.
All it knows it to look at a small area of disk, load the data into memory and attempt to run the program. This program is the boot loader and in this case it is the lilo boot loader.
In the same way, when the lilo boot loader runs it doesn't know which filing system or operating system is in use so it can't find lilo.conf. It can't find the kernel image either by file name but it has information on where the kernel file is on the disk. This information is given to it when /sbin/lilo is run.
So if you create a new kernel image and copy it to /boot with the same name as the old image it might not be in exactly the same place on the disk as before nor might it be the same size.
But when you run /sbin/lilo it looks at lilo.conf and then recreates the boot loader with the location of every kernel image referenced in lilo.conf.

Excellent! Thank you all for helping me understand this.