Ubuntu – Install Ubuntu on Second Hard Drive whilst Leaving Unallocated Space for Use by Other Operating Systems


Just as a preface I have read the following question,

Install on Second Hard Drive with startup boot option?

which is similar however my question is slightly more specific so I don't feel this is a duplicate.

I have 3 hard drives – a 256GB SSD with Windows 10 installed on it, a 512GB SSD with various files I use from Windows on it and a 2TB mechanical. The 512GB SSD will be my target drive to install Ubuntu on.

This drive already has data on it in a ~360GB partition, with ~120GB of space unallocated. Can I simply install Ubuntu in this 120GB unallocated space without touching the data on the 360GB partition*?

From various sources it seems this is not an option as I'll likely need to delete any current partitions and create a new partition table on this drive. So, with that in mind, would that still allow me to create a partition on Windows on this drive using space not reserved for Ubuntu or any of its partitions?

* If this is an option then would this still allow me to create an EFI partition on which to install the bootloader such that I can set the boot priority of this drive to the top allowing me to choose OS to load upon start-up as can usually be done?

Best Answer

    1. Let us assume that you bought the computer with Windows installed in UEFI mode.

    2. Let us also assume that you want to install Ubuntu for this particular computer (not a portable system, that can work in any computer). If this is not correct, please tell me, and I will change the answer.

    3. I also assume that you mean unallocated space (outside any partition). Or do you mean free space within the data partition?


    Installing in UEFI mode will let you select partitions (the standard is one root partition '/' and one swap partition) whereever you want and there is unallocated space or prepared partitions for Ubuntu. But it will select the already existing EFI partition (in your case in the Windows drive).

    So it is no problem to install in the unallocated space alongside your data partition in the second SSD.

    But if you want to play safe, you should back up all really important files to some other drives, because partitioning and installing operating systems is risky, and it is easy to make a mistake.

    Boot from the Ubuntu install drive and use gparted to create a root partition and a swap partition for Ubuntu. If the drive has an MSDOS partition table (not GPT), you might start by creating an extended partition of all the free space, and create Ubuntu's partitions inside it.

    Start the installer, and at the partitioning window, select Something else alias manual partitioning, and select the partitions that you prepared with gparted. The bootloader will automatically go into the existing EFI partition.


    This might work directly or you might have to fix the UEFI boot depending on the computer. Some UEFI systems to not comply with the standard for UEFI, and it creates problems with dual booting. If there are problems with booting, please specify the computer brand name and model. If there are problems later on, for example with the graphics, please specify the graphics chip/card (also brand name and model).


    See these links and links from them for booting in UEFI mode.

    booting with UEFI

    UEFI Installing - Tips