How to Multi-Boot Linux
A Simplified View
by Merlin Whitewolf
The first consideration in creating a multi-boot set up is hard disk size. Your HDD must be of sufficient size to contain all of the distributions that you wish to install. Twenty GB is of sufficient size to comfortably boot two distros. More distros could be added, but updating them might become an issue. From thirty GB and up, you would have more options for adding more distros.
Note: Hard disks can have only four primary partitions on them. If you plan to have more partitions, you'll need an extended partition.
The first thing you'll need to do is set up your partitions. PCLinuxOS has a partitioning tool in the PCLinuxOS Control Center (PCC) > Mount Points tab, or you may want to use a partitioning tool like the GParted live CD. The tool you use should be the one you are most comfortable with. If you have not used one before, either of the two named above is a good one to start with. As I have used GParted more often, I will describe its use below. The partitioning tool in PCC is just as useful though.
Insert the live CD in your CD drive and start your computer. Be sure that your BIOS has been set to boot from the CD. Set up of GParted is intuitive, so follow through the set up menus until the partitioning interface is loaded.
Important: If you're starting with Windows installed, be sure you run the disk defragmenter in Windows before you partition the drive, if you want to keep Windows. Why? When Windows is writing a file to the disk, it looks for a suitable piece of free space in which to store it. Lets say you modify an existing file, adding a whole bunch of data so the file now takes up more space on the disk. To accommodate the file, Windows writes the first part of the file in one section of the disk and then scouts around for other places to store the rest of the file. The end result is that a single file may be stored in several chunks scattered about the disk. Running the disk defragmenter allows Windows to gather all the scattered pieces and put them back together at the beginning of the partition. If you were to partition the drive without defragmenting, you would risk losing data that was spread all around the disk.
To resize your Windows partition, click to highlight it and choose "Resize/Move" on the toolbar. (Windows partitions are ntfs or fat32.) In the box that opens, you'll see a bar with a colored border and three sections of numbers; the first is "Free Space Preceding." This should have a "0" in it. Next is the size of your drive in MB. This is the number that you will be changing. Last is "Free Space Following." This will show the amount of space you will free up.
On the triangle to the right of the bar, left click and hold. Drag your cursor to the left to reduce the size given in the middle number dialog to your desired size. This size is up to you, but you'll want to have more space than Windows has in use for safety. The amount that Windows has used is shown in yellow on the bar. A good rule of thumb is to keep your Windows partition 10 GB or more. On my 160 GB drive, I gave it 29 GB, but, I have lots of space.
Click the "Resize" button. Click "Apply" on the toolbar. You will be asked to confirm your choice.
When resizing has been completed, you'll see an unassigned area of your drive in grey, listed just under your Windows partition. Click to highlight it and then click "New" on the toolbar. The size may be chosen by the method described above. The file system can be chosen on the right. Click on the button with "ext2" on it and choose "ext3". Click "Create" and then "Apply". Your new partition will be created and then appear on the list. Use this method to create as many partitions as you need.
To create a swap partition (virtual memory), choose "Linux Swap" from the file system type menu. A Swap partition of 1 GB is a good compromise. If you plan to remaster your system, create a 2 GB swap partition.
If you plan to have more than four partitions, create one of the four primary partitions as an extended partition by changing "Primary Partition" to "Extended Partition" in the New box. This is located just above the file system type chooser. This will create the partition on all of the remaining space on your drive. You may create as many "Logical" partitions as you would like within it. Note that Logical partition numbers will begin at five.(hda5)
When creating your partitions, be sure to size them to hold what you will be putting on them plus extra space for updates, adding applications, and for your files and folders. For your main distro, you may want to have separate /home and root (/) partitions. You may do this for all installations, or you may choose to install each distro using one partition per distro. Be certain that other distros do not use your main /home partition. Also, you will need to write each of these partition numbers down because you will need them later.
When you install the bootloader of your main distro, choose the "install to MBR" option. Install the other bootloaders to the root partition of each distro. Be aware that some distros install to the MBR by default without asking you to choose. Find out how to change this before you proceed, if no options are easily available.
To add an entry to your bootloader, open PCC and click on "Set up How the System Boots". When the wizard opens, click next if you are not making changes to the way that PCLinuxOS is booted. On the following page, click "Add" to add another listing to your grub menu. You'll need to know the partition number on which you installed root. (You should have this written down already.)
You should find out the kernel version number of the distro and be prepared to enter it. Example: 2.6.18.6.dev3.lgc is the kernel version in PCLOS 94 RC1. An entry for it would be:
linux /boot/vmlinuz-2.6.18.6.dev3.lgc /dev/hda5 splash=silent
Alternatively, you could open a terminal, type "su" and enter. Give your root password when asked and then type "kwrite /boot/grub/menu.lst".When the editor opens, scroll to the bottom and make an entry, maybe something like this:
title Mepis rootnoverify (hd0,7) chainloader +1
Important: Be sure to have an empty space between entries in your /boot/grub/menu.lst.
Grub numbering begins with 0, so your first hard drive will be hd0. Any additional hard drives will be numbered from 1 on up. Partitions are also numbered in this manner by grub. Thus your first partition on your first HDD will be hd0,0.
Note: SATA drives will be sd rather than hd.
For more information on grub, consult the grub manual at:
http://www.gnu.org/software/grub/manual/grub.html
GParted live CD is available for download at:
http://gparted.sourceforge.net/livecd.php
Enjoy your multi-booting experience.