now, before you tell me to use the search function for this (common) issue - i did work an this for the last 5 hours and i am getting to no (close) solution.

This is the exact problem:
After updating my 12.04 to 14.04 yesterday booting ended up in the GRUB rescue prompt. So i did what i did often before when facing boot problems (and it worked every time until yesterday!): i got a live usb-device installed and ran boot-repair but this time this made it worse: my bios is now not even recognizing the hard-drive (SATA) as bootable.

Running boot-repair a few times more with different settings did not help. Then i searched all the forums and wikis on how to install grub manually and what i found was this:

1. boot into a live system


2. mount the 'broken' system, especially the /sys, /proc and /dev directories


3. chroot into this system


4. (re-)install the correct grub-package (which is grub-efi-amd64 for me)


5. run update-grub


6. exit the chroot


7. reboot

But this still leaves me with my hard-drive not beeing recognized (and as a result with a "operating system not found" error)

. The partitioning is the following:

/dev/sd?

  /dev/sd?1: 94MB, flags: boot, fat16

  /dev/sd?2: 2GB, linux-swap

  /dev/sd?3: ~260GB, ext4, the rest of the ubuntu 14.04

As of my naive view, i always thought this is the way it works:

1. My bios sees the hard-drive and the partition with the boot flag


2. The bios (whether efi or legacy does not matter to me, it has to work) launches grub there


3. Grub loads the linux-kernel from the third partition

I insist on the separate boot-partition because - as i said - this is not the first time for me to experience big issues with GRUB. The separate partition made solving it easier for me.

I'll - of course - provide any information neccessary. Thanks in advance!