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Old 01-09-2011, 07:14 AM   #1
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Disk Partitions for dual boot with Windows 7 GPT/EFI

I have a Centos 5.5 system that had 2 primary partitions (2nd is setup as LVM with multiple LVM partitions) and then installed Windows 7 as Dual Boot.
However, Windows 7 has installed a 200MB system partition which is GPT/EFI as partition 3 and the Win7 OS as a Primary Partition.
I have a heap of space undefined after this fourth primary partition.
However, as 4 primary partitions have been used, I can no longer create an extended partition to utilise this.
As such I would like to know what is the best and safest way to proceed, and if possible step by steps instructions for the best option eg:
1. Delete the Windows 7 System Partition and create the extended partition (I expect this will prevent Windows from booting)
2. Use something like partition magic to change the Win 7 OS Partition 4 to an extended partition (Not sure if this will work)
3. Make changes to the overall system including both Linux and Windows so that it will use GPT only (I have had no experience with GPT so this is a bit scary)
4. Other?


Old 01-09-2011, 03:18 PM   #2
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Option 1 and 2 would work with windows inside the extended partition. You just have to write the grub config stanza to fool win7 into believing it's on the first partition (remapping the partitions on the fly. you can find more about that in the grub manual).

Option 3 I don't know anything about.

Option 4 (other). Make a full backup of your Linux installation. Reformat that partiton for ntfs and install win7 there. Then delete the 4th primary partition (now with win7) and make an extended partition. Then install Linux inside that extended partition, then restore the backup.

Then reconfigure your LVM as needed to be able to use it from Linux in the extended partition.

I suggest doing it that was because GNU/Linux is imminently more adaptable and able to boot from partitions other than the first on the hard drive, than Micro$oft Windows could ever be. That's a personal bias arrived at by using both OSs, and settling on the easiest to use.

Last edited by bigrigdriver; 01-09-2011 at 03:22 PM.
Old 01-10-2011, 06:22 PM   #3
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Smile Solved - change Windows 7 OS from primary to logical partiion

Thanks mate
After finding that the Windows Recovery DVD will not find Windows on an extended or primary partition unless the "system partition" is there, I did the following to resolve for now for anyone else that has the same problem:

Booted to a Live DVD with partition imaging and partition management software
Backed up the system partition to file
Removed the system partion so only 3 primaries existed
Created extended partition
Created a logical partion and imaged across from the Windows OS primary partition to this
Removed the Windows OS Primary Partition
Re-created the windows 100MB system partition and restored the previous image to this
Restarted pc and booted to Windows 7 DVD
Entered the repair option
It made the necessary changes to the bcd on the recovery partition
System now boots windows 7 OS from the logical partition via the bcd on the 100MB windows primary partition

I am still yet to move the linux lvm from primary to extended but will do this when I have more time.


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