Fixing “error: file not found” and “grub rescue” after Ubuntu update

When you update your Ubuntu installation, you may occasionally encounter issues such as the “error: file not found” message followed by the “grub rescue> _” prompt. This error typically occurs due to a misconfigured or corrupted bootloader. In this article, we will explore several solutions to fix this issue.

Solution 1: Use Boot Repair

Boot Repair is a simple tool that can fix these types of issues. Here’s how to use it:

1. Boot Ubuntu from a LiveCD or Live USB. This will allow you to run Ubuntu without installing it on your computer, which is necessary because the error prevents you from booting into your installed Ubuntu system.
2. Connect to the internet. Boot Repair requires an internet connection to download the necessary packages.
3. Open a terminal. You can do this by pressing Ctrl + Alt + T.
4. Add the Boot Repair PPA. In the terminal, run the following command:

sudo add-apt-repository ppa:yannubuntu/boot-repair && sudo apt-get update

This command adds the Boot Repair Personal Package Archive (PPA) to your system’s software sources, and then updates your package list.

5. Install Boot Repair. Run the following command in the terminal:

sudo apt-get install -y boot-repair && boot-repair

This command installs Boot Repair and then launches it.

6. Use Boot Repair. Follow the instructions provided by the tool. For more detailed instructions, refer to the official Boot Repair documentation.

Solution 2: Manually fix the bootloader

If you’re comfortable with terminal commands, you can manually fix the bootloader. Here’s how:

1. Enter the grub rescue prompt. If you’re seeing the “grub rescue> _” prompt, you’re already there.
2. List the partitions. Type ls and press Enter. This command will display a list of partitions on your hard drive.
3. Set the prefix. Enter the following command, replacing (hd0,msdos6) with the appropriate drive/partition from the list you obtained in the previous step:

set prefix=(hd0,msdos6)/boot/grub

This command sets the path that grub uses to find its modules.

4. Load the normal module. Type insmod normal and press Enter. This command loads the normal module, which provides the normal command.
5. Get the boot prompt back. Type normal and press Enter. This command will bring back the regular grub boot prompt.
6. Log into Ubuntu and fix the bootloader. Once you’ve booted into Ubuntu, open a terminal and run the following commands:

sudo grub-install /dev/sda
sudo update-grub

The first command installs grub to your hard drive (replace /dev/sda with your actual hard drive), and the second command updates the grub configuration file.

Solution 3: Use SuperGrub and BootRepair

SuperGrub is a bootable CD that can help you boot into your system when you’re having trouble with your bootloader. Here’s how to use it:

1. Create a boot CD using SuperGrub. Download SuperGrub, burn it to a CD, and boot your computer from this CD.
2. Boot into your system. Use the options provided by SuperGrub to boot into your Ubuntu system.
3. Download and use BootRepair. Follow the instructions in Solution 1 to download and use BootRepair.

Solution 4: Check the boot order in BIOS

Sometimes, the problem is as simple as having the wrong boot order in your BIOS settings. Here’s how to check and fix this:

1. Access the BIOS settings. The method to do this varies depending on your computer’s manufacturer. Generally, you’ll need to press a specific key (like F2, F12, Del, or Esc) during the boot process.
2. Check the boot order. Look for a section in the BIOS settings called “Boot Order” or something similar. Make sure that the first boot disk is set to the Linux OS disk.

Solution 5: Unplug USB drives

If you encounter the error after upgrading and have a USB drive plugged in, try unplugging the USB drive and rebooting. Sometimes, the presence of a USB drive can confuse the bootloader.

In conclusion, there are several ways to fix the “error: file not found” and “grub rescue” issues after updating Ubuntu. The method you choose depends on your comfort level with terminal commands and your specific system configuration. Always remember to back up your data regularly to prevent data loss in case of system errors.