Trying to dual boot Ubuntu 14.10 with Windows 10, last one not detected

I wasn't able to get the boot repair to work so I manually added a Windows 10 boot option.

The first step is to edit /etc/grub.d/40_custom (using SUDO) and add the following lines to the bottom of the file:

menuentry 'Windows 10' {
set root='(hd0,msdos1)'
chainloader +1
}

In this case my bootloader was in /dev/sda1 hence the 1 at the end of msdos. After this run sudo update-grub2 and you should be good to go.

Worked for me, advice taken from here: http://technologytales.com/2010/11/21/manually-adding-an-entry-for-windows-7-to-an-ubuntu-grub2-menu/

Windows should be detected while you manually install Ubuntu 14.10 and added to GRUB. If it is not added initially, boot into Ubuntu, install Boot Repair and run that. That should add Windows 10 to your GRUB.

Source: I have run a Windows 10, Ubuntu 14.10, elementary OS, Fedora quad boot

I had the same problem with Windows 7 after an Ubuntu 15.04 install.

The solution was to use Grub 2 ntloader module instead of chainloader.

Here is my 42_custom in /etc/grub.d/

menuentry "Win 7 (loader) (on /dev/sda1)" --class windows --class os {
insmod part_msdos
insmod ntfs
insmod ntldr
set root='(hd0,msdos1)'
search --no-floppy --fs-uuid --set=root 9804BD3004BD126C
ntldr ($root)/bootmgr
}

You can change the text to Windows 10, it's only text.