5.1. Why build a custom kernel?

Building a custom kernel is one of the most important rites of passage every Unix system administrator must learn. This process, while time-consuming, will provide many benefits to your FreeBSD system. Unlike the GENERIC kernel, which must support every possible SCSI and network card, along with tons of other rarely used hardware support, a custom kernel only contains support for your PC's hardware. This has a number of benefits:

• It will take less time to boot because it does not have to spend time probing for hardware which you do not have.

• A custom kernel often uses less memory, which is important because the kernel is the one process which must always be present in memory, and so all of that unused code ties up pages of RAM that your programs would otherwise be able to use. Therefore, on a system with limited RAM, building a custom kernel is of critical importance.

• Finally, there are several kernel options which you can tune to fit your needs, and device driver support for things like sound cards which you can include in your kernel but are not present in the GENERIC kernel.