Boot-Repair is around from quite sometime, released under license GNU-GPL and it is great tool to fix the issues with your Grub and Boot, it repair frequent boot issues you may encounter in Ubuntu like when you can’t boot Ubuntu after installing Windows or another Linux distribution, or when you can’t boot Windows after installing Ubuntu, or when GRUB is not displayed anymore, some upgrade breaks GRUB, etc. Boot-Repair lets you fix these issues with a simple click, which (generally re-installs GRUB and) restores access to the operating systems you had installed before the issue.
Boot-Repair also has advanced options to back up table partitions, back up bootsectors, create a Boot-Info (to get help by email or forum), or change the default repair parameters: configure GRUB, add kernel options (acpi=off …), purge GRUB, change the default OS, restore a Windows-compatible MBR, repair a broken filesystem, specify the disk where GRUB should be installed, etc.
Boot-Repair will create a Ubuntu pastebin link for you to share that allows experienced members to see what’s wrong with your boot. Ubuntu’s Pastebin is not easily indexable or searchable, and purpose of the tool which creates this page (Boot-Info) is meant to be a very helpful solution to the problem.