How do I get back Grub Bootloader back if it has suddenly disappeared?

Question

I was using Ubuntu 17.04 and had to install some packages but I was encountering some errors(like Error 404) and I wasn't also able to update apt-get so I followed this online tutorial and made some changes in the sources.list after which I was able to update apt-get and install the packages. However on restarting my PC now it directly goes to Windows 10 without showing the bootloader like it used to do

Answer 1

You cannot get back into Linux ?

Is Windows located on a separated hard-disk ?

You could re-install with 18.04 LTS in expert-modus - but only re-install the root-files in the root-partition of '/' - and do not format the previous /home - Partition of your linux and also do not format the windows-Partition. This way grub will be reinstalled too (into MBR of sda? - or into MBR of root-harddisk) and update-grub2 will be done automatically.

This way Windows will be accepted and your previous Linux-/home partition will be taken over.