My computer setup is:

  • 1- SSD 120GB
  • 1- HDD 320GB
  • 1- HDD 1TB

I have two partitions on SSD of Windows 10 (one for work, another for games/testing/whatever) and I want to install Ubuntu on my 320GB HDD. However, Ubuntu installer doesn't recognize Windows.

I tried to select "More options" to make the partitions on my own but when installer start said "errno 5 input/output" I redownloaded ISO, tried other pendrives and every USB connection of my PC but always the same error.

Is there anything I can do?


I managed to install Ubuntu on my 320GB hard drive but now GRUB is not detecting Windows10 partitions.

I tried to use Boot-repair but despite "successfully boot repaired", only Ubuntu appears in GRUB.

Here is a pastebin of Boot-repair log: http://paste.ubuntu.com/p/5KbYMRxqg9/

  • /sda (windows system partitions)
    • /sda1 Windows 10 Work partition
    • /sda2 Windows 10 Fun partition
    • /sda3 Windows Reserved Partition
  • /sdb (Storage)
  • /sdc (Ubuntu)
    • /sdc1 Ubuntu 18.04
    • /sdc2 /Boot (partition recommended by Boot-repair)

Any ideas?

  • Are you sure you are installing Ubuntu in the same mode (UEFI vx. legacy) as Windows? – ubfan1 May 15 '18 at 20:12
  • 1
    You need to make sure Windows 10's fast start up is off. askubuntu.com/questions/843153/… You probably need that off, just to have both Windows work. Post these: sudo fdisk -lu and sudo gdisk -l /dev/sda and then for sdb & sdc. – oldfred May 15 '18 at 20:33

With multiple drives and BIOS boot, best to only run Boot-Repair's advanced mode. Then you can choose to only install grub2's boot loader to the MBR of the Linux drive. You ran the auto fix which installed grub to the MBR of all drives. You will want the Windows boot loader in sda & grub in sdc. Boot loader in sdb does not matter.

Windows normally installs a separate Boot partition with bootmgr & BCD. Windows users do not see it as it is not shown in Windows. It normally is a 100MB partition just before the main install, but you have the main install at beginning of drive, sda. So Boot partition must have been on the now Linux drive. You can have bootmgr & BCD in your main Windows install if you have the boot flag on the main install which you do have and fix Windows.

But you cannot fix your issues with Linux repair tools, you need a Windows repair flash drive or installer with repair console and run the full set of Windows repairs, to add bootmgr, BCD and Windows boot loader to MBR of sda.

This is a Linux forum, so if you need help on fixing Windows use



I had a similar issue back then when I was installing Ubuntu alonside Win7 & Win10, I made it through:

  1. Installing Ubuntu on a separate partition .
  2. After installation I found that grub won't read Windows Installations, tried sudo upgrade-grub but still no resolution.
  3. Found a utiltity named boot-repair and it did the work.

Thank you to @oldfred to guide me to the right path. I solved this way


  1. Download Windows 10 ISO from Microsoft Webpage
  2. Create a bootable USB using Unetbootin
  3. Boot Windows 10 USB and select "Repair" -> "Advanced Options" -> "Command Prompt"
  4. Insert the following commands to delete partitions including Ubuntu:

Start diskpart utility


Select the disk X where you want to install Windows Boot Manager and Ubuntu 18.04

list disk

select disk X

Erase disk and partitions


convert disk to gpt

convert gpt

Create partition efi 260mb and format as fat 32

create partition efi size=260

format quick fs=fat32

Check that everything is correct

list partition

Note the volume letter where the Windows OS is installed.

list volume

Exit from diskpart utility


Rebuild Windows Boot Manager

bcdboot X:\windows Note: Replace "X" with the volume letter of the Windows > OS partition.

In my case, I had to use it twice. One for Work partition and another for Games partition.

  1. Install Ubuntu as normally do in the same disk as Windows Boot Manager.

Now, when you start your computer Grub2 will ask you if you want to start Ubuntu or Windows Boot Manager.

  • Sounds like you converted to a new UEFI install. Windows only boots from gpt with UEFI and only from MBR with BIOS. And then if UEFI better to have all drives as gpt and all installs as UEFI. – oldfred May 16 '18 at 18:27

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