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Champ
Asked: 2016-01-13 12:39:16 +0800 CST

How to regenerate grub menu entries on Ubuntu 14.04 Trusty after deleting all kernels?

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I accidently removed all kernels from my Ubuntu 14.04 Trusty. I followed steps in this question's answers to install a new kernel but when I try to boot I don't see the 'Linux/ubuntu' option in my grub menu list. It only shows 'System Settings'.

How do I regenerate the earlier/default menu entries for ubuntu in grub?

Note:

  1. I am currently able to boot with these steps on grub prompt:

    set root=(lvm/ubuntu--vg-root)
linux /boot/vmlinuz-3.13.0-74-generic root=/dev/mapper/ubuntu--vg-root
initrd /boot/initrd.img-3.13.0-74-generic

    boot

  2. When on live usb, I copied vmlinuz, init... etc. from my boot partition to /boot folder because I could not find a way to use a separate boot partition from grub prompt.

14.04

2 Answers

  1. You can manually boot with a separate /boot.

    Separate /boot on sda1, / on /dev/mapper/ubuntu--vg-root:

    set prefix=(hd0,1)/grub
insmod linux
set root=/dev/mapper/ubuntu--vg-root
linux (hd0,1)/boot/vmlinuz-3.13.0-74-generic root=/dev/mapper/ubuntu--vg-root
initrd (hd0,1)/boot/initrd.img-3.13.0-74-generic
boot

    Not sure why BobaJob's instructions were down voted. If you can boot and fstab still has separate /boot that would reinstall grub to MBR. And a sudo update-grub regenerates menu. Or use dpkg to reinstall grub. If from live installer you can also use Boot-Repair.

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  2. sudo grub-install /dev/sda

    Something like that should fix it, assuming your main HDD is /dev/sda.

    If you've booted from a Live CD/USB you'll need to chroot first.
    http://howtoubuntu.org/how-to-repair-restore-reinstall-grub-2-with-a-ubuntu-live-cd

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