6. Several ways of obtaining the kernel

We have spoken so far about the client and server's configuration for operation after the BOOTP request has been issued by the client, but the first problem is that most computers are not able to behave as BOOTP clients by default. We will see in this section how to fix this.

6.1. BOOTP or DHCP capable NICs

This is the most simple case: some network cards provide a supplement to the BIOS, containing a BOOTP or DHCP client, so just setup them for BOOTP or DHCP operation in the BIOS, and you're done.

6.2. Kernel on a local floppy or hard drive

These cases are also quite simple: the kernel is loaded from a local drive, and all the kernel has to do is to obtain its network parameters from BOOTP, and mount its root filesystem over NFS; this should not cause any problem. By the way, a local hard drive is a good place to leave a /var, /tmp, and a /dev...

If you have a local hard drive, all you have to do is to use lilo or your favourite boot loader as usual. If you use a floppy, you can use a bootloader or simply write the kernel on the floppy: a kernel is directly bootable.This enables you to use a command like the following:
      # dd if=zImage of=/dev/fd0 bs=8192

However, Alan Cox told in a linux-kernel thread that this feature of the linux kernel will be removed sooner or later, you thus will have to use a bootloader even on floppies some day. I know this still works with 2.4.11 kernels, but support seems to have been removed in the 2.4.13 version. See the sixth chapter of the boot-disk-HOWTO for this topic.

6.3. Bootloader without kernel on a local floppy or hard drive

Certain bootloaders are network aware, you may thus use them to download the kernel image from the network. Some of them are listed below:

6.4. Creating ROMs for the clients

Many network cards include a slot in which one can insert an EPROM with additional BIOS code. This enables one to add, for instance, BOOTP capabilities to the BI0S. To do so, you will first have to find how to enable the EPROM socket. You may need a jumper or a special software to do so. Some cards like the 3Com 905B have slots for EEPROMs which enable one to change the software in the EEPROM in place. In appendix, you'll find the information about EPROM and various types of memory chips.

For a list of EPROM burner manufacturers visit the Yahoo site and go to economy->company->Hardware->Peripherals->Device programmers or check out the old Diskless-HOWTO List of EPROM burner manufacturers section.

If you choose to create your own ROMS, you will have to load a BOOTP or DHCP capable software in the ROM, and then, you will be in the case of BOOTP or DHCP capable NICs described above.

You will also need to find the proper EPROM size and speed for your NIC. Some methods to do so are provided in appendix, because the NICs manufacturers often do not provide this information.

6.5. Local CDROM

This section was originally written by Hans de Goede for the Diskless-root-NFS-HOWTO. I modified it slightly in order to reflect some differences between this document and the Diskless-root-NFS-HOWTO.

Much of the above also goes for booting from cdrom. Why would one want to boot a machine from cdrom? Booting from cdrom is interesting everywhere one wants to run a very specific application, like a kiosk, a library database program or an internet cafe, and one doesn't have a network or a server to use a root over nfs setup.

6.5.1. Creating a test setup

Now that we know what we want to do and how, it's time to create a test setup:

6.5.2. Creating the CD

If you need more information than you can find below, please refer to the CD-Writing-HOWTO.