Why Bother?

The kernel that comes with Red Hat Linux works for most hardware and software applications. But there are several good reasons why you might want to change your kernel:

Drivers You want to take advantage of a new driver. It may be for hardware that you just installed, or for a filesystem that you want to try.

Bugs You ve learned that your current Linux kernel does not work in some way that affects how you run this operating system.

Features You ve heard about a new kernel. Perhaps it provides improved hardware support, such as for an IEEE 1394 FireWire video recorder. Maybe it allows you to connect to an 802.11a wireless network.

Security You may want to protect yourself against a newly discovered security breach.

Size It s possible to speed up your system by removing unneeded drivers, thereby reducing the size of your kernel.

When you want to change your kernel, you should consider the following options, in order:

1. Recompile your existing kernel. New kernels and associated source code can consume a lot of space. A newer kernel may not work as well with the software you have in place. You may be able to do what you need with the existing kernel.

2. Patch your existing kernel. You can perform small upgrades of Linux kernels with a patch. When applied, the patch is incorporated into your current kernel source code. For example, a single patch can upgrade your kernel from version 2.4.20 to 2.4.21.

3. Install a new kernel. Once the new kernel package is installed, you should also configure and compile the new kernel.

Kernel Version Numbers

Linux kernels are stored in the /boot directory with a name such as vmlinuz-2.4.23 . All kernels include a version number in a major.minor.patch numbering format. In this case, the first number (2) refers to the second major release of the Linux kernel. The second number (4) has two meanings: it s the fourth minor release of the specified major kernel, and since it s an even number, it s a production-ready version of the kernel. The third number (23) refers to the twenty-third patch to the specified minor release.

Red Hat Linux kernels have version numbers that look slightly different, such as 2.4.23-10. You can see that there s an extra number; this is the build number. Each build can incorporate a small number of new drivers or bug fixes. Some Red Hat kernels include a number with a pp, a pre-patch, which is a test release of a kernel.

If you re installing a new kernel on a production computer, avoid odd minor numbers; for example, kernel version 2.5.22 is a beta release not suitable for the real world. In addition, pre-patch (pp) kernel releases may also be fraught with risk.