Building a Kernel

Now it is time to build a kernel. For the target system we will build a kernel that is different from the host system kernel. We build it under the myboot directory. First cd to the myboot/linux-2.4.21 subdirectory.

The most important job is configuring the kernel. Run the following command:

make menuconfig

Instead of menuconfig you can use config (not recommended!) or xconfig. This will give a usable kernel for the target system.

• Processor type menu: processor family must be 486, switch off SMP support, leave the rest at defaults.
• General setup menu: switch off hot-pluggable devices, system V IPC and sysctl support. Support ELF binaries, other formats can be disabled.
• Parallel port support can be switched off, unless you want to enable it for PLIP networking or parallel port storage devices (ZIP disk, CD-ROM).
• SCSI: enable SCSI CD-ROM support, enable a large selection of low level drivers as modules.
• Network device support: enable a large selection of Ethernet cards as modules.
• Code maturity, Module support, Memory Technology, Parallel port, Plug and play, Multi-device, Telephony, I2O, Amateur radio, ISDN, Old CDROM, Input core, Multimedia, Sound, and kernel hacking submenus: disable everything, if it was not already disabled.
• Block device submenu: support floppy, loop device, RAM disk and initial RAM disk.
• ATA/IDE/MFM/RLL submenu: support, keep everything under the ATA/IDE... block devices submenu the default.
• Character devices submenu: Support virtual terminal, console on virtual terminal, Unix 98 PTY, disable everything else.
• File systems. Keep second extended, proc and dev PTS enabled. If you want to mount DOS diskettes, enable fat, msdos and vfat. Enable iso9660, NFS (client only) and ext3. If you want to experiment with other file systems such as reiserfs, you must enable support for them.
• Console drivers. Keep VGA text console enabled.
• Exit and say Yes to save changes.

Of course you must adapt the configuration to the target system you are using are you are anticipating your target audience to use. This kernel tries to be useful for a large number of systems, from 486DX onward. The strategy is to keep things in if they enable a user to get started with an installation, so it must be possible to access SCSI harddisks and CD-ROMs and also the local area network in case the machine does not have a CD-ROM. This kernel will be different from the one that is going to be used after installation. Support for soundcards and printers is probably unnecessary on this installation disk.

Now we only need to build the kernel:

make clean
make dep
make bzImage

The kernel described here should be around 900kB.

Next create the modules:

make modules
make INSTALL_MOD_PATH=$MYBOOT modules_install
cd $MYBOOT
tar zcvf modules.tar.gz lib

The modules will end up in a compressed tar archive, not normally stored on the main RAM disk.