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I have an existing system with Windows 7 64 bit installed on one HDD. System is BIOS ROM. There is a second HDD, no OS just files. Both are formatted with Windows partitions.

I want to add Ubuntu 16.04 to make a dual-boot system. I don't want to change the existing Windows installation.

Using the installer on the Live CD, after adjusting the partitions on the second HDD, can I install Ubuntu on the second HDD?
Will this keep the existing Win7 installation unchanged?

As for selecting which OS to boot, which HDD will the MBR be on? And will it still operate correctly to select which OS on startup?
Or would it be better to select the OS by setting the HDD boot order in ROM?

Any other considerations or flaws with this plan? And part that couldn't be done using the Live CD installer?

Asaf M
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user3169
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  • YES: grub handles this (i'm assuming 'bios rom' means legacy over uefi/efi). your BIOS will control which hdd boots, it should point to drive where MBR is setup with grub. If you install as is, the ubuntu install will overwrite the MBR used by windows so indirectly** windoze will be touched (your windoze media will undo this if you have it), so one option is to make the other HDD the boot drive, then install ubuntu & grub to that one; then your windoze hdd will be completely untouched. ** i use indirectly as the windoze partition isn't altered, but users often think mbr=touched.. – guiverc Oct 22 '17 at 23:33
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    Possible duplicate of Dual Boot Windows 10 and Linux Ubuntu on Separate Hard Drives – karel Aug 04 '19 at 13:57

2 Answers2

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You may install Ubuntu on any volume in your system, as long as you install GRUB to the drive the system boots from. As noted in comments, one way to avoid making any changes to the Windows drive (allowing easiest return to single-boot Windows-only operation) is to change the boot order in your BIOS settings to make the empty drive primary, then install Ubuntu on the empty drive. During installation, Ubuntu will set up GRUB to boot Windows, so you can still use Windows, but if you want to return to "one OS" operation, just change the boot order back (so the Windows drive is primary).

I had that setup for several years on my desktop machine (the one I'm answering from), so can confirm it works.

Zeiss Ikon
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  • Upvoting this and not @Taiko 's answer because this is easier and more elegant. End result is the same though, as long as you do this https://askubuntu.com/questions/967811/can-ubuntu-16-04-windows-7-be-set-up-as-dual-boot-on-seperate-hdds#comment1568129_967899 –  Nov 16 '17 at 05:04
  • Finally got around to doing this (with 18.04). Worked like a charm. My only addition is that I created an unallocated partition in Windows Drive Management out of free space at the end of the non-Windows OS HDD. The Ubuntu installer had no problem setting to ext4 and installing there. – user3169 Jan 07 '20 at 00:07
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If you're able to you could keep the Windows HDD unplugged during the Ubuntu installation. Then each drive will have its own MBR and bootloader which you could switch using the bios.

This method makes it easier to uninstall either operating system later as you won't have to worry about fixing any broken bootloaders.

Taiko
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  • Are you saying "unplugged during the Ubuntu installation" and after that leave both plugged in? In normal operation I have files I need to access on both drives, so both need to be powered on. – user3169 Oct 23 '17 at 16:38
  • @user3169 Yes. After installation you would then plug the Windows HDD back in. Then you can access it from Ubuntu like normal. – Taiko Oct 25 '17 at 01:21
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    And for this configuration it's better to set BIOS to boot Ubuntu and then run sudo update-grub. Windows should now be detected and added to the Grub menu. From then on you'll be able to select Windows from the Grub menu and no need to keep changing the boot order at BIOS. –  Nov 16 '17 at 05:00