https://help.ubuntu.com/community/Boot-Repair
Boot-Repair
Boot-Repair is a simple tool to 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 reinstalls 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 is a free software, licensed under GNU-GPL.
Getting Boot-Repair
1st option : get a disk including Boot-Repair
The easiest way to use Boot-Repair is to create a disk containing the tool (eg Boot-Repair-Disk, a disk starting Boot-Repair automatically), and boot on it.
Remark : it is recommended to install the ISO on a live-USB (eg via UnetBootin or LiliUSB or Universal USB Installer). Do not burn it on a DVD if your computer has Windows8 pre-installed, or if your boot is in EFI mode.
2nd option : install Boot-Repair in Ubuntu
- either from an Ubuntu live-session (boot your computer on a Ubuntu live-CD or live-USB then choose "Try Ubuntu") or from your installed Ubuntu session (if you can access it)
- connect to the Internet
- open a new Terminal, then type the following commands (press Enter after each line):
sudo add-apt-repository ppa:yannubuntu/boot-repair
sudo apt-get update
sudo apt-get install -y boot-repair && (boot-repair &)
Using Boot-Repair
Recommended repair
launch Boot-Repair from either :
the Dash (the Ubuntu logo at the top-left of the screen)
or by typing ‘boot-repair‘ in a terminal
Then click the "Recommended repair" button. When repair is finished, note the URL (paste.ubuntu.com/XXXXX) that appeared on a paper, then reboot and check if you recovered access to your OSs.
If the repair did not succeed, indicate the URL to people who help you by email or forum.
Advanced options
Warning: the default settings are the ones used by the "Recommended Repair". Changing them may worsen your problem. Don‘t modify them before creating a BootInfo URL, and asking for advice on Ubuntu Forums Absolute Beginners Section or in Installation and Upgrades.
External Links
Official website of Boot-Repair
Topic "Boot-repair: Graphical tool to repair the PC boot in 1 click !" - on Ubuntu forum, for any questions/comments.
HOWTO : easily create a Boot-Info summary