Ubuntu – How to edit grub for many entries of previous kernels with multiple ubuntu installations

Hold down Shift key after selecting Ubuntu. Press E to edit grub entries manually if you know how. Then Ctrl+X to boot.

If you don't know how to edit the grub entries, press C to get to a grub prompt. Then enter the following:

search -s -f -n /ubuntu/disks/root.disk
probe --set=diskuuid -u $root
loopback loop0 /ubuntu/disks/root.disk
set root=(loop0)
linux /vmlinuz root=UUID=$diskuuid loop=/ubuntu/disks/root.disk ro quiet splash
initrd /initrd.img
boot

After booting, enter sudo update-grub to fix grub.cfg.

The Boot Repair tool is increasingly making a hash of things by creating too many backup copies of too many boot loader files. There are numerous ways to solve this problem. Here's one of them:

1. Back up your EFI System Partition (ESP), which is /dev/sda1 in your case and is mounted at /boot/efi. A file-based backup (using tar or cp, for example) should do fine. This will enable you to recover should things go badly.
2. Install my rEFInd boot manager. This is most easily done by installing the Debian package.
3. Reboot. rEFInd should appear and show you boot options for Ubuntu and Windows.
4. Test each of the rEFInd options in turn, taking note of the filename specified under each and what it does. (A few may lack such filenames. One with a Windows icon will probably be one of these, but it will probably launch GRUB.) Be sure you can boot both Linux and Windows from rEFInd.
5. In Linux, open a shell and change to the /boot/efi directory, which is the EFI System Partition (ESP), where boot loaders are stored.
6. Delete the boot loaders that didn't work when you tested them, or copy them into a backup location (say, /boot/efi/backups). Do likewise with duplicates -- if two boot loaders both launched GRUB, for instance, you can delete or move one of them.
7. Move the boot loader that actually launched Windows (if it was identified by filename in rEFInd's main menu) to /boot/efi/EFI/Microsoft/Boot/bootmgfw.efi. This is where it's supposed to belong. Boot Repair copied it to another filename, so you're just copying it back.
8. If you can boot Linux directly via a vmlinuz-3.5.0-23-generic entry, you can probably delete GRUB, or uncomment the dont_scan_files line in /boot/efi/EFI/refind/refind.conf and add grubx64.efi to its list.

If all goes well, you should now be booting via rEFInd, which should present you with a much smaller list of boot options. If there are still too many, you can try to track down the errant files and delete them, if you think that's appropriate, or use the dont_scan_files, dont_scan_dirs, or dont_scan_volumes options in /boot/efi/EFI/refind/refind.conf to keep the remaining items out of the boot list. Such "blacklisting" might be helpful to keep links from /vmlinuz to /boot/vmlinuz-3.5.0-23-generic out of the boot list, if your system has such a symbolic link.

Note that rEFInd scans for boot loaders on every boot, so it will automatically pick up new kernels when you install them.

If you prefer to keep using GRUB, you can do something conceptually similar to my procedure, but you'll need to peruse the /boot/grub/grub.cfg file and cross-reference this to your notes on which boot loader entries work and which don't work to discover which files to delete. You'll then need to use update-grub to re-write your grub.cfg file. Your current grub.cfg file also has BIOS-mode entries for launching Windows, which are useless, and I'm not sure how to keep update-grub from picking them up, if indeed that's how they got in there.

Good luck!