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In theory, what I want to do is very simple, but I've done some google research and read some posts on this site and I'm still confused.

I want to keep win7 on my primary C:\ drive, and install Ubuntu (12.10) on a secondary drive (that I have yet to buy or install. I just want to be certain that I'm successful when I do this). If at all possible I'd also like it if when I start the computer I have the option to boot either Win7 or Ubuntu, like an account log in type thing where I just pick which drive I'm running with that day. And just to reiterate, I do not want to partition my C:\ drive or alter, change, or affect my Win7 system in any way.

The reason I'm still fairly uncertain about all of this, is that a lot of the guides I've read have been for earlier versions of Ubuntu. Also the vast majority of guides are about partitioning one drive to fit both OS'. I want two separate OS running from two separate drives that I can pick at boot. The guides I did find mentioned that there is some issue with the grub being installed on C:\ but the rest of the OS being installed on the other drive. Is this still the case? How do I avoid that?

Also, if it helps, I've been running 12.04lts on my laptop for a few months now in and out of class and I love it.

Finally, if you could please point me to a guide or write your answer in the form of a guide for a two year old that'd be awesome. I'm still an Ubuntu novice and I don't want to mess up my win7.

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up vote 13 down vote accepted

How it works

Each partitioned disk contain one small block called MBR. It resides at the beginning of the disk.

Now, OS insert their code to MBR to load their own booloader. Windows does same, linux does same.

They insert a small code pointing to actual location of bootloader. Like in linux, This MBR contains Stage1 of GRUB (GRUB is a booloader used in linux) which loads a larger executable Stage2 that may located in other partition.

If you install Windows, and then linux, GRUB stage1 sits in MBR. Now other part of GRUB (the actual booloader) contains Windows Booloader location. Now when you select Windows from GRUB menu, windows starts to load. This is called chain loading (GRUB loads first, then GRUB loads windows booloader based on selection).

Coming back to your question

So for your case, you have two MBR (because you have 2 hard disk).

You have two option

Easiest one

  • Create a partition on 2nd disk.
  • Install ubuntu on that parition & install GRUB on 2nd disk's mbr not on first disk's mbr. Be careful here. See below image (just for demo purpose), you need to do everything in (probably) sdb.

  • You select your already created sdb partition, edit, assign mount point /, and file system type ext4

  • Select boot loader location as sdb , not sda (see red colored section)


  • Once done, reboot and you will be booted to windows 7.

It happens because, your boot disk priority says to boot from first harddisk (Where we didn't change anything).

So open BIOS, change boot disk priority so that the disk containg ubuntu comes first.

  • This time, GRUB will be loaded. And you can boot either OS.

  • Remove the disk, windows 7 will boot directly.

  • Again plugin the 2nd disk, verify boot order from BIOS so that 2nd disk comes first. You can now boot any OS again.

Another way

You can modify Windows booloader also to load ubuntu from 2nd disk. It is a bit harder, and since you don't want to touch windows 7 at all, I am not recommending it.

Note: All tutorials available here talks about adding ubuntu from same disk but different partition. I have not done it for across devices, you may need to adopt accordingly.

Here is tough guide to do so.

There is a great GUI tool to edit boot loader called EasyBCD (It is free for personal use). Their guide about setting up ubuntu using windows bootloader.

You can have more resource on it Easy BCD Help: Dual boot Win7 and Ubuntu 11.10 -- "Add new Entry" for Ubuntu

I strongly recommend using GRUB as bootloader,as it is more flexible.May be you can set windows as default boot option AND/OR reduce timeout value.

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Okay, so I'd first have to format the new drive (ubuntu) and then create a partition on said drive. Then install linux on sdb1 and the grub to sdb? Also, If its easy.. I'd like the computer to prompt me to pick a disk on startup.. so if that means editing even windows bootload I'd be willing to think about it.. :D – Arammil Mar 28 '13 at 10:28
@Arammil When you boot from sdb, GRUB will come up first and promt you to choose between Windows (take you to sda) or Ubuntu (in sdb) just as you want. You don't have to change the setting in BIOS every time for that. – user68186 Mar 28 '13 at 10:34
yes you got it correct, just one thing you create partition if you need some part of hard disk to be available to windows. Or else you don't need to create partition. 2nd question : No disk selection is possible, as much as I know.. it depends on the BIOS. And pick up disk prompt is not equal to editing windows boot loader. I will add some guide for editing windows thing. – Web-E Mar 28 '13 at 10:35
Well windows will be my main OS on this system, so is there a way that I can get the windows bootloader to prompt me to boot either Win7 or Ubuntu like grub will? Or if I use Grub to boot windows, will both disks be constantly running? – Arammil Mar 28 '13 at 10:43
You can set windows as default on to boot using grub. If you boot windows & don't use disk2, most probably it will suspend the disk for power saving. It all depends on OS. Nothing can be done here. – Web-E Mar 28 '13 at 10:57

Easiest way to do this is as suggested above. First, temporarily remove your first hard drive (the one with Windows on it). Second, install Linux to the second hard drive (which for now is the only one connected). Third, put your first hard drive back in, so that you now have two hard drives installed, each with its own OS. From there, it's a simple matter of pressing a key at boot to select your boot drive. For example, with a Dell machine you'd push the F12 key at boot, and this would bring up your menu to select the drive you want to boot from.

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Disconnect your first drive with the Win 7 on it. That way you will be safe. Your computer probably has a boot selector function in it. Take a look in the setup and see that it is enabled.

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The user specifies what he'd recommend. Unless you have factual evidence stating that he shouldn't keep his W7 hdd installed, you should try to contribute to the answer. – Hellreaver May 3 '15 at 7:52

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