Slackware Linux Essentials
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7.3 Dual Booting

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Many users set up their computers to boot Slackware Linux and another operating -system. We've described several typical dual boot scenarios below, in case you are having -difficulty setting up your system.

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7.3.1 -Windows

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Setting up a computer with both MS Windows and Linux is probably the most common dual -boot scenario. There are numerous ways you can setup the booting, but this section will -cover two.

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Often times when setting up a dual boot system, a person will devise a perfect plan -for where everything should go but mess up the installation order. It is very important -to understand that operating systems need to be installed in a certain order for a dual -boot setup to work. Linux always offers control over what, if anything, gets written to -the Master Boot Record. Therefore, it's always advisable to install Linux last. Windows -should be installed first, since it will always write its booter to the Master Boot -Record, overwriting any entry Linux may have put there.

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7.3.1.1 Using LILO

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

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Let's say you have a 40GB 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.

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-   20GB   Windows boot (C:)
-   1GB   Linux root (/)
-   19GB  Linux /usr (/usr)
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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. Adequate swap space is the discussion of -many flames on IRC and Usenet. There's no truly “right” way to do it, but -sticking with the rule above should be sufficient.

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With your partitions laid 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.

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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.

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Reboot the computer. LILO should load and will display a menu letting you select -between the operating systems you have installed. Select the name of the OS you wish to -load (these names were selected when you setup LILO).

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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.

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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.

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7.3.1.2 Using LOADLIN

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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.

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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.

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After installing the operating systems, copy the loadlinX.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:

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

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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.

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-C:\> cd \
-C:\> attrib -r -a -s -h MSDOS.SYS
-C:\> edit MSDOS.SYS
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Add this line to the file:

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-BootGUI=0
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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:

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-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
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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.

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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.

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7.3.1.3 Deprecated Windows NT -Hack

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This is the least common dual booting situation. In the days of old, LILO was unable -to boot Windows NT, requiring Linux users to hack NTLDR, which presented several more -problems than dual booting between Windows 9x and Linux. Understand that the following -instructions are deprecated. LILO has been able to boot Windows NT/2000/XP/2003 for many -years now. If you are using a legacy machine though, you may need to use just such a -hack.

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Install Windows NT
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Install Linux, making sure LILO is installed to the superblock of the Linux -partition
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Get the first 512 bytes of the Linux root partition and store it on the Windows NT -partition
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Edit C:\BOOT.INI under Windows NT to add a Linux option
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Installing Windows NT should be fairly straightforward, as should installing Linux. -From there, it gets a little more tricky. Grabbing the first 512 bytes of the Linux -partition is easier than it sounds. You will need to be in Linux to accomplish this. -Assuming your Linux partition is /dev/hda2, issue this -command:

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-# dd if=/dev/hda2 of=/tmp/bootsect.lnx bs=1 count=512
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That's it. Now you need to copy bootsect.lnx to the Windows NT partition. Here's where -we run into another problem. Linux does not have stable write support for the NTFS -filesystem. If you installed Windows NT and formatted your drive as NTFS, you will need -to copy this file to a FAT floppy and then read from it under Windows NT. If you -formatted the Windows NT drive as FAT, you can simply mount it under Linux and copy the -file over. Either way, you will want to get /tmp/bootsect.lnx -from the Linux drive to C:\BOOTSECT.LNX on the Windows NT -drive.

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The last step is adding a menu option to the Windows NT boot menu. Under Windows NT -open a command prompt.

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-C:\WINNT> cd \
-C:\> attrib -r -a -s -h boot.ini
-C:\> edit boot.ini
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Add this line to the end of the file:

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-C:\bootsect.lnx="Slackware Linux"
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Save the changes and exit the editor. When you reboot Windows NT, you will have a -Linux option on the menu. Choosing it will boot into Linux.

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7.3.2 -Linux

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Yes, people really do this. This is definitely the easiest dual boot scenario. You can -simply use LILO and add more entries to the /etc/lilo.conf -file. That's all there is to it.