This would be the most interesting post in the grub series – if you have read the previous ones and you are in the above situation.
* Grub wont show up – shows an error and grub_resuce>
* Cannot do boot repair – as the live disc is booting only in Legacy mode – and UEFI entry for the USB drive is missing from the boot menu 
* Linux was successfully installed somewhere on your drive – and you forgot where – and you want to boot that one.
I am personally attaching a few screenshots to add beauty to the steps. These are taken from my Virtualbox – where linux was installed as legacy.
* You would have a grub rescue terminal similar to this one:
* Find the partition where you installed Linux
grub > ls (hd0) (hd0,msdos5) (hd0,msdos4)
If your partition is a GPT one. ie OS was installed as UEFI : you would find something like :
grub > ls (hd0) (hd0,gpt5) (hd0,gpt4)
grub > ls (hd0) grub > ls (hd0,gpt5)
grub > ls (hd0,msdos1) Filesystem type ext2 - Last modiifcation date : blahblah
The ext2 type of partition shows that you have probably hit the right one. To ensure that:
grub > ls (hd0,msdos1)/
Yay ! That looks similar to a standard Linux ‘/’ partition. So you would get that your linux resides in (hd0,msdos1).
* Start the boot procedures.
Before we start – let me copy paste a standard grub:
We will have to give roughly similar params to make sure that our grub boots right.
grub> set root=(hd0,msdos1) grub> linux /boot/vmlinux-3.2.x.x root=/dev/sda1 grub> initrd /boot/initrd.img-3.2.x.x grub> boot
Hint: You can find out the proper root=/dev/sda1 with a trick.
(hd0,msdos1) means /dev/sda1.
(hd0,msdos2) means /dev/sda2.
(hd1,msdos1) means /dev/sdb1.
(hd0,gpt1) means /dev/sda1.
Thats it ! Hit enter – and you will see your installed linux booting !! Yay!
You will find out how to re-install grub in the next post !