I have Windows 10 on an SSD in a DVD caddy (/dev/sdb) and Ubuntu mate on an HDD (/dev/sda). Both are Legacy BIOS/MBR on a Dell Laptop.
I made a dual boot set up and tested putting GRUB on the Linux disk /dev/sda and again tried with GRUB on /dev/sda1. I used EasyBCD to add the location of GRUB to the Windows Bootmgr.
With this set up when I turn on my laptop the Windows 10 boot menu gives me the choice of Windows 10 and Ubuntu.... IF I choose Ubuntu my laptop first does a quick reboot then I get a GRUB2 menu where I can choose Ubuntu or Windows.
Can Windows Bootmgr just load Ubuntu without needing a second reboot? Is there anyway to make this happen? Other methods or boot managers?
What I have tried
I tried placing the Ubuntu bootloader code in /dev/sda and also in /dev/sda1. I was thinking that putting the GRUB2 stuff in a partition might allow Windows to load the Linux OS without needing an extra boot after I select Ubuntu from the Windows bootmgr menu.
What I read elsewhere
GRuB can load Windows without rebooting. The grub bootloader can only be loaded by the system BIOS when the computer boots.
It seems that dual booting Windows and Linux involves "Chain Loading". But does chain loading always require extra reboots?
GRUB2 can load Windows without needing an extra reboot. Can Windows Bootmgr load Ubuntu without needing a second reboot?