Most kernels are compiled with loadable modules. Current Linux distributions, including RHEL, configure modules in the initial RAM disk, which is compiled into a initrd-* file in the /boot directory. As you can see in the GRUB configuration file, the initial RAM disk is normally associated with the last line in a GRUB configuration stanza. As described in topic 8, you can create a new initial RAM disk configuration file with the mkinitrd command. But errors are also possible, as you'll see in the following exercise.
For this exercise, you'll need a partner. Have your partner make changes to your system. As your partner works to create a network problem for you to solve on your computer, look away until the computer is rebooting.
It's most helpful if you have a VMware snapshot of your RHEL system. Problems like those created in this exercise have caused administrators to mess up their systems in other ways. You'll also need the first RHEL installation CD.
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Back up the configuration file associated with the boot loader, /boot/grub/grub.conf. Make sure to back up this file to a non-standard location, in case your partner also backs up any files before changing them.
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Open the /boot/grub/grub.conf configuration file in a text editor. Focus on the initrd command line, which might look like the following:
initrd /initrd-2.6.18-8.el5.img
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Misspell both initrd words in this line.
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Reboot the system, and let your partner back at the computer. Tell him or her to address the error message shown. Give your partner the first RHEL 5 installation CD.
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Make sure to tell your partner to back up any files that he or she might change to the appropriate home directory.
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Whatever happens, restore the original /boot/grub/grub.conf configuration file when your partner is finished with this exercise. (Alternatively, you can restore the configuration from a VMware snapshot.)