Setting up a CD-R or CDRW drive on an IDE PC in Debian GNU/Linux 3.0 ("Woody")
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3. Changing the kernel

You can skip this section if you can detect the ide-scsi module using lsmod (see SCSI emulation in the previous section). Otherwise, you must install a kernel with the ide-scsi module. The pre-compiled kernel images are supplied as .deb packages on the official CDROMs. A safe choice is kernel-image-2.2.20.

3.1. Precautions

3.1.1. Master boot record (mbr)

If you have other operating systems on your PC, or you are using a boot-loader such as Partition Magic, you must be careful not to write to the master boot record (mbr). If you do write to the mbr, you may find that systems such as Windows NT will not boot. You will have to repair them with the system's "emergency repair disc" or "recovery disc", or restore the mbr from a backup copy (see below). You do not have to worry about this if you are using LILO to boot your other operating systems.

Warning

Make sure that you have an up-to-date emergency repair disc for systems such as Windows NT.

You can make a backup copy of your existing mbr to floppy disc as a precaution. Put a formatted floppy in drive f0 and use the following command to copy the mbr from hard drive hda. (You must have root permissions.)

athlon:/home/chris# mount /floppy
athlon:/home/chris# dd if=/dev/hda of=/fd/MBR bs=512 count=1
athlon:/home/chris# umount /floppy

You can restore the mbr from the floppy using this command:

athlon:/home/chris# dd if=/fd/MBR of=/dev/hda bs=446 count=1

See /usr/share/doc/lilo/Manual.txt.gz for more details.

3.1.2. Debian boot floppies

You must be able to boot back into Debian if the installation goes wrong. You can do this from the Official Binary CDROMs providing that they are bootable on your PC. Now would be a good time to try. Boot your PC with the Official Binary CD in your CDROM drive. Press F3 at the boot: prompt, and read about the RESCUE option.

Alternatively, you may have made a boot floppy when you originally installed Debian. If not, you can make an up-to-date boot floppy during this installation. Make sure that you have a floppy disc ready.

3.2. Installing the new kernel

You can check which pre-compiled kernels are available using apt-cache.

athlon:/home/chris# apt-cache pkgnames | grep kernel-image | more

A good choice is to install "kernel-image-2.2.20", because it includes the "ide-scsi" module. Use apt-get to start the installation process.

athlon:/home/chris# apt-get install kernel-image-2.2.20
A new kernel has been installed at /boot/vmlinuz-2.2.20
Would you like to create a boot floppy now? [No]

Enter y if you would like to create a boot floppy, and follow the instructions.

Would you like to create a boot floppy now? [No] y

Now you need to install a boot block. This makes your system bootable from the hard drive. If Debian is the only operating system on your PC, you can probably accept the default answers. If you have other operating systems and a boot manager other than lilo you must be careful not to install a boot block in the mbr nor to make your Linux root partition active.

My system has other operating systems on /dev/hda1, /dev/hda2 and /dev/hda5. The Linux swapspace is on /dev/hda6 and the Debian root is on hda7. My boot manager expects to boot Debian Linux from partition /dev/hda7. This is what I have to enter:

Install a boot block using the existing /etc/lilo.conf [Yes] n
Wipe out your old LILO configuration and make a new one? [No] y
Do you wish to set up Linux to boot from the hard disk? [Yes] y
Install a partition boot block on partition /dev/hda7? [Yes] y
Make /dev/hda7 the active partition? [Yes] n

You should be able to work out your needs by looking at this listing. See /usr/share/doc/mbr/README and documents in /usr/share/doc/lilo for more details

3.3. If things go wrong

If you find that you want to re-install this kernel, you will have to make it available to apt-get again by un-installing it

This command un-installs the kernel image:

athlon:/home/chris# dpkg --purge --force-remove-essential kernel-image-2.2.20

This command regenerates the apt cache and displays a list of kernel images in the regenerated cache:

athlon:/home/chris# apt-cache --generate search kernel-image | more
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