Dual Booting

Using LILO

Most people will want to use LILO to chose between Linux and Windows. As stated above, you should install Windows first, then Linux.

Let's say you have a 47GB IDE hard disk as the only drive in your system. Let's also say that you want to give half of that space to Windows and half of that space to Linux. This will present a problem when trying to boot Linux. I do not know the specific geometry of the drive, but chances are that 23.5GB down the drive will be well past the 1024th cylinder. A better layout for this drive would be:

 
   1GB   Windows boot (C:)
   1GB   Linux root (/)
   22.5  Windows misc (D:)
   22.5  Linux /usr (/usr)
         

You would also want to set aside an adequate amount of space for a Linux swap partition. The unwritten rule is to use twice the amount of RAM you have in disk space. A 64MB system would have 128MB of swap, and so on.

With your partitions layed out, you should proceed to install Windows. After that is set up and working, you should install Linux. The LILO installation needs special attention. You will want to select the “expert” mode for installing LILO.

Begin a new LILO configuration. You will want to install it to Master Boot Record so that it can be used to choose between the two operating systems. From the menu, add your Linux partition and add your Windows (or DOS) partition. Once that's complete, you can install LILO.

Reboot the computer. LILO should load and wait for user interaction. You can press Alt to get the boot: prompt. Type the name of the operating system you want to load (these names were selected when you setup LILO). If you forgot the name, press Tab to get a list of operating systems that you can boot.

You can configure LILO even further by editing the /etc/lilo.conf file on your Linux partition. You can set it up to display a text menu, and always present the prompt. For example, if I wanted my LILO display to do this:

   System Boot Menu
   ================
   1 - Linux
   2 - Windows

   LILO boot:

My /etc/lilo.conf file would look like this:

   # LILO configuration file

   boot = /dev/hda
   vga = normal
   message = /boot/message

   image = /vmlinuz
      root = /dev/hda2
      label = 1
      read-only

   other = /dev/hda1
      label = 2
      table = /dev/hda

And my /boot/message file would look like this:

   System Boot Menu
   ================
   1 - Linux
   2 - Windows

LILO is quite a configurable boot loader. It's not just limited to booting Linux or DOS. It can boot just about anything. The man pages for lilo(8) and lilo.conf(5) provide more detailed information.

What if LILO doesn't work? There are instances where LILO just won't work on a particular machine. Fortunately, there is another way to dual boot Linux and Windows.

Using LOADLIN

This method can be used if LILO doesn't work on your system, or if you just don't want to set up LILO. This method is also ideal for the user that reinstalls Windows often. Each time you reinstall Windows, it will overwrite the Master Boot Record, thus destroying any LILO installation. With LOADLIN, you are not subject to that problem. The biggest disadvantage is that you can only use LOADLIN to boot Linux.

With LOADLIN, you can install the operating systems in any order desired. Be careful about installing things to the Master Boot Record, you do not want to do that. LOADLIN relies on the Windows partition being bootable. So during the Slackware installation, make sure you skip the LILO setup.

After installing the operating systems, copy the lodlinX.zip (where “X” is a version number, such as “16a”) file from root's home directory to your Windows partition. Also copy your kernel image to the Windows partition. You will need to be in Linux for this to work. This example shows how to do this:

   # mkdir /win
   # mount -t vfat /dev/hda1 /win
   # mkdir /win/linux
   # cd /root
   # cp loadlin* /win/linux
   # cp /vmlinuz /win/linux
   # cd /win/linuz
   # unzip loadlin16a.zip
         

That will create a C:\LINUX directory on your Windows partition (assuming it's /dev/hda1) and copy over the necessary stuff for LOADLIN. After doing this, you will need to reboot into Windows to setup a boot menu.

Once in Windows, get to a DOS prompt. First, we need to make sure the system is set to not boot into the graphical interface.

   C:\>cd \
   C:\>attrib -r -a -s -h MSDOS.SYS
   C:\>edit MSDOS.SYS
         

Add this line to the file:

   BootGUI=0
         

Now save the file and exit the editor. Now edit C:\AUTOEXEC.BAT so we can add a boot menu. The following provides an example of what a boot menu block in AUTOEXEC.BAT would look like:

   cls
   echo System Boot Menu
   echo.
   echo 1 - Linux
   echo 2 - Windows
   echo.
   choice /c:12 "Selection? -> "
   if errorlevel 2 goto WIN
   if errorlevel 1 goto LINUX
   :LINUX
   cls
   echo "Starting Linux..."
   cd \linux
   loadlin c:\linux\vmlinuz root=/dev/hda2 ro
   goto END
   :WIN
   cls
   echo "Starting Windows..."
   win
   goto END
   :END

The key line is the one that runs LOADLIN. We tell it the kernel to load, the Linux root partition, and that we want it mounted read-only initially.

The tools for these two methods are provided with Slackware Linux. There are numerous other booters on the market, but these should work for most dual boot setups.