System Administration 176 Getting Started Guide Re-Compiling the Linux Kernel Because OpenLinux includes full source code for the operating system kernel, you can recompile the kernel if the need arises. Reasons to do this include: • Adding patches or updates to the kernel • Adding additional hardware support • Enabling a core feature (such as IP firewalling) that was disabled by default Re-compiling the kernel isn’t as difficult as it sounds. Depending on your sys- tem’s speed, re-compiling may take less than 10 minutes or several hours. (A Pentium 200 MHz with 32 MB of RAM takes about 10 minutes for re-compil- ing.) You must have the kernel source code packages and supporting development tools installed on your OpenLinux system before using this procedure. To re-compile the Linux kernel: 1. Log in as root 2. Make a backup copy of the current kernel using a command like this one: cp /vmlinuz /vmlinuz.backup CAUTION: Don’t name the backup kernel vmlinuz.old; that name is already used internally by the kernel. 3. If you don’t have a diskette to boot from in case of problems, add a section to your /etc/lilo.conf file so that you can boot from the vmlinuz.backup kernel that you created in the last step. (If you don’t have a bootable diskette, you can create one using the dd command.) 4. Run the /sbin/lilo program to update the lilo boot loader if you have changed /etc/lilo.conf. 5. Change to the /usr/src/linux directory. cd /usr/src/linux 6. Depending on which tool you want to use to reconfigure the kernel, enter one of these commands: • make config to start a command-line interface that queries you (Yes/No) for each kernel option. This is best for those who are already familiar with the kernel compilation process.