Dual boot with Windows

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Revision as of 20:50, 18 March 2011 by KerrickStaley (Talk | contribs) (Windows and Arch Dual Booting: 10 GB is not at all enough; I started out with a 20GB / and am almost out of space, and I don't have that many programs installed. I changed it to recommend 25GB.)

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This is a simple article detailing different methods of Arch/Windows coexistence.

Windows and Arch Dual Booting

In this example, we will install Windows first, and subsequently install the GRUB bootloader along with Arch, allowing for dual boot.

Installation will be standard, but there are a few things to keep in mind:

1. You may have to use logical partitions for some of our partitions, because there can only be up to 4 primary partitions per disk.

2. Remember to write down your partitions numbers: "sda1, sda2... sda8", noting which type of partitions belong to their relevant number. For example:

sda1 
Windows - 30GB should be enough. Many new games exceed 10GB each so bear this in mind.
sda2 
/boot - 100MB is enough (optional)
sda3 
/ - about 25GB is appropriate
sda4
swap - between 1024MB and 1512MB (optional)
sda5
/home - use rest of hard drive (optional)

It is important to note that there is a 1024 cylinder limit with some older BIOSs. This means that the BIOS cannot access things beyond the 1024th cylinder (about 8.5GB), so the /boot partition should be in the first 8.5GB (space before Windows partition). GParted LiveCD or a partitioning tool in SystemRescueCd are useful for moving and resizing partitions to accommodate this.

3. When installing grub, you must configure /boot/grub/menu.lst), and make sure to install grub to /boot (or root (/) if you did not create a separate partition for /boot). Installing grub onto your Windows partition may cause Windows not to boot. There should be about three lines at the end of the file that speak about chainloading to boot other OSs, these can most generally be uncommented if you follow above convention, this would place windows boot point at hd0,0 or sda1. Thus you would have something akin to this:

Note: The above instruction is conflict with the GRUB installation position documented in GRUB#General notes about bootloader installation which says GRUB should be installed to MBR or the first partition to be recognized by most BIOS.
Note: It is also possible to install GRUB to MBR (dev/sda). This works fine with Windows 7.
# Windows XP
title Windows XP
rootnoverify (hd0,0)
chainloader +1

The parts of this entry break down as follows:

title Windows XP 
Can be anything you like, it will just be what is displayed in the grub bootup screen
rootnoverify (hd0,0) 
Remember the partition numbers we wrote down, here you write in the partition number of your windows partition. This sets the windows boot at root, even though GRUB cannot read it.
chainloader +1 
What this does is call the Windows boot loader that is still in MBR in our case, since GRUB cannot boot Windows itself.
  • The file is read from the top down, so the system listed first will be the one to auto boot, if no keys are pressed during the grub boot screen.
  • GRUB uses a zero indexed system of numbering drives and partitions, which is a different convention than you may be used to seeing:
First disk, first partition=sda1=hd0,0
First disk, second partition=sda2=hd0,1
Second disk, first partition=sdb1=hd1,0

Dual Booting from Multiple Hard Drives

To dual boot from two separate hard drives (e.g., one dedicated Linux drive and one dedicated Windows drive) and Windows is not on the first hard drive, the Windows boot loader must be "tricked" into thinking Windows is on the first hard drive. Do this by adding the following lines to your menu.lst config file:

map (hd0) (hd1)
map (hd1) (hd0)

So the entry for Windows on second disk, first partition will look like this:

title Microsoft Windows XP Professional
root (hd1,0)
savedefault
makeactive
map (hd0) (hd1)
map (hd1) (hd0)
chainloader +1

Or if the above configuration doesn't work, you might try the one below from the Arch Wiki GRUB page:

title Windows
map (hd0) (hd1)
map (hd1) (hd0)
rootnoverify (hd1,0)
makeactive #if you use Windows7 this line should be commented out
chainloader +1

More information on GRUB configuration can be found in the GRUB manual.

Other Layouts

1. You could use:

sda1 
Windows XP
sda2 
swap
sda3 
root
sda4 
home

and not use an extended partition (as /boot will be in the / partition as well).

2. LVM (Linux Volume Management) is also a possibility to use. You could simply create a single LVM partition and let it create the other partitions inside it. This allows a single partition to hold all your needed GNU/Linux data, and allows to easily partitions when necessary.

Notes on /home

You may not wish to store you documents on this mountpoint, especially if you wish to share data between both Windows and Arch Linux. Historically, this was done on a FAT partition because writing to NTFS was still experimental. NTFS-3G now offers stable writing to NTFS partitions, so you can just leave this as another partition that will be shared by both Windows and arch. Another option would be to use some of the tools in Windows, such as fs-driver and use an ext3 or ext2 partition to store documents (fs-driver will mount ext3 partitions as ext2, so you will not be able to take advantage of journaling while in Windows).

Using Windows boot-loader

Another option is sort of the reverse of what is described at the beginning of this article where GRUB loads the Windows boot loader, which then loads Windows. Under this option, the Windows boot loader load GRUB, which then loads arch.

Using Windows 7 Boot-Loader

Excerpted from http://www.iceflatline.com/2009/09/how-to-dual-boot-windows-7-and-linux-using-bcdedit/

This assumes you have already resized your Win partition, created Linux partitions, and installed linux. Some documents state that the partition being loaded by the Win boot-loader must be a primary partition but I have used this without problem on an extended partition.

  • When installing the grub bootloader, install it on your /boot partition rather than the MBR.
    Note: For instance, my /boot partition is /dev/sda5. So I installed grub at /dev/sda5 instead of /dev/sda
  • Under linux make a copy of the boot info by typing the following at the command shell:
my_windows_part=/dev/sda3
my_boot_part=/dev/sda5
mkdir /media/win
mount $my_windows_part /media/win
dd if=$my_boot_part of=/media/win/linux.bin bs=512 count=1
  • Boot to windows and run cmd with administrator privileges (navigate to Start->All Programs->Accessories, Right-click on Command Prompt and select “Run as administrator.”)
bcdedit /create /d “Linux” /application BOOTSECTOR
  • BCDEdit will return an alphanumeric identifier for this entry that I will refer to as {ID} in the remaining steps. You’ll need to replace {ID} by the actual returned identifier. An example of {ID} is {d7294d4e-9837-11de-99ac-f3f3a79e3e93}.
bcdedit /set {ID} device partition=c:
bcdedit /set {ID}  path \linux.bin
bcdedit /displayorder {ID} /addlast
bcdedit /timeout 30

Done! Reboot and enjoy. In my case I'm using the Win bootloader so that I can map my Dell Precision M4500's second power button to boot linux instead of windows.

Using Windows 2k/XP Boot-Loader

For information on this method see http://www.geocities.com/epark/linux/grub-w2k-HOWTO.html. I do not believe there are any distinct advantages of this method over the linux boot-loader, you will still need a /boot partition, and this one is arguably more difficult to setup.