How to Fix Ubuntu Not Booting: Step-by-Step Guide Using Boot Repair

By 佐川 直弘 | Naohiro Sagawa (運営者)

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1. When Ubuntu Won’t Boot: Common Issues and Why You Need Boot Repair

What Happens When Ubuntu Fails to Start?

After using Ubuntu for a while, you might one day find that it suddenly won’t boot. You could get stuck on a black screen, see a “grub rescue” prompt, or experience a total freeze — the symptoms vary. In most cases, this is due to an issue with the bootloader (GRUB). The operating system itself might be intact, but the “entrance” needed to start it isn’t working properly.

These kinds of boot problems can be caused by the following:

• Corruption or deletion of GRUB configuration files
• Changes to disk layout (e.g., partition editing, replacing SSD)
• Conflicts in dual-boot setups with Windows
• Changes to UEFI/BIOS settings
• Problems following a kernel update

What Is Boot Repair? Your Lifesaver During Boot Issues

This is where Boot Repair comes in. It’s a free tool that helps fix boot errors in Ubuntu and other Linux distributions. With just a few clicks, it can detect and repair GRUB issues automatically — no command line needed.

This is especially helpful for beginners who prefer not to use the terminal. If Ubuntu fails to boot, don’t panic or jump straight to reinstalling — give Boot Repair a try first.

Why You Should Know About Boot Repair

Boot problems can strike without warning. For users unfamiliar with Linux, it’s often hard to figure out what went wrong or what to do next. But if you know about Boot Repair, you can fix most issues in just a few minutes — no reinstall required.

As you continue reading, you’ll learn how to use Boot Repair step-by-step. Once you’re done, you’ll be ready to handle boot failures calmly and enjoy a more stress-free Linux experience.

2. What Is Boot Repair? Features and Capabilities

What Exactly Is Boot Repair?

Boot Repair is a powerful tool designed to fix boot issues in Ubuntu and other Linux distributions. It specializes in repairing the GRUB bootloader (GNU GRUB), and one of its biggest advantages is that you don’t need to be familiar with the command line — everything is done through an easy-to-use graphical interface (GUI).

If your system stops at a black screen or shows errors like “no such partition” or “grub rescue,” Boot Repair can help restore boot functionality quickly.

Key Features

Boot Repair comes with a range of useful features:

• Reinstall GRUB (grub-install)
• Automatically reinstalls GRUB when it’s broken or missing
• Regenerate GRUB configuration (update-grub)
• Detects installed operating systems and rebuilds boot menu entries
• Repair the MBR (Master Boot Record)
• Restores the MBR in legacy BIOS systems if it’s been corrupted
• Fix EFI boot entries
• Restores EFI partitions for systems using UEFI boot mode
• Generate a Boot Info Report
• Creates a detailed URL-based report that can be shared on forums for support

Supported Operating Systems and Environments

Boot Repair works in the following environments:

• Ubuntu 12.04 and newer (including recent LTS versions like 22.04)
• Debian-based derivatives like Linux Mint and Zorin OS
• Both BIOS (legacy) and UEFI boot modes

Note that in UEFI mode, you need to ensure the correct EFI partition is mounted. We’ll cover this in more detail when we walk through the installation steps later in this guide.

How Is It Different from Other Repair Methods?

What makes Boot Repair stand out is its intuitive graphical interface. Traditionally, fixing GRUB requires a series of manual steps like:

1. Booting into Ubuntu via a Live USB
2. Using the terminal to run mount and chroot
3. Manually executing grub-install and update-grub

These steps can be daunting for beginners, and mistakes are easy to make. Boot Repair simplifies the process and allows you to fix boot issues with just a few clicks, making it a reliable and stress-free solution.

3. Getting Started with Boot Repair: How to Install It

Prepare a Live USB: Create an Environment Where Ubuntu Can Boot

If your system can’t boot into Ubuntu, you won’t be able to install Boot Repair the usual way. That’s why you first need to create a Live USB and temporarily boot into Ubuntu from it.

A Live USB is a USB drive containing the Ubuntu installer, allowing you to boot and use Ubuntu without installing it on your hard drive — perfect for troubleshooting.

Quick Steps:

1. On another working computer, download the Ubuntu ISO image
2. Use a tool like Rufus or balenaEtcher to write the ISO to a USB drive
3. Change the BIOS/UEFI settings of the broken PC to enable USB boot and start from the Live USB
4. Select “Try Ubuntu” to enter the desktop environment without installing

Note: The official Ubuntu website provides detailed instructions for creating a Live USB.

How to Install Boot Repair

Once you’re running Ubuntu from the Live USB, open a terminal and install Boot Repair. You’ll need an internet connection via Wi-Fi or Ethernet, so make sure your device is connected before proceeding.

Installation Commands:

sudo add-apt-repository ppa:yannubuntu/boot-repair
sudo apt update
sudo apt install -y boot-repair

After running these commands, Boot Repair will be installed in your Live environment and ready to use.

Important Notes for Offline Environments

Boot Repair can launch without an internet connection, but some features will be limited. For example, downloading the latest packages or uploading logs online won’t work offline. Whenever possible, use it with internet access for the best results.

If you can’t connect to the internet, there’s an alternative: use the “Boot-Repair-Disk” ISO, which comes with Boot Repair pre-installed. You can boot directly into this environment from a USB drive or CD, making it a handy offline option.

4. How to Use Boot Repair: Recommended Repair Steps

Launching Boot Repair and Understanding the Main Interface

Once you’ve booted into Ubuntu from your Live USB and installed Boot Repair, you’re ready to start the recovery process. Boot Repair has a simple GUI (Graphical User Interface), so even users uncomfortable with the terminal can use it with ease.

To launch Boot Repair:
Open a terminal and enter the following command:

boot-repair

After a moment, a window will appear and automatically scan your system. When the scan finishes, you’ll see two main options:

• Recommended repair
• Advanced options

For first-time users or beginners, it’s best to choose “Recommended repair” for a safe and automatic fix.

Automatically Repair GRUB Using “Recommended Repair”

“Recommended repair” detects and fixes common issues — such as broken GRUB files or missing boot entries — with minimal user input.

Steps:

1. Click the “Recommended repair” button
2. The repair process starts and a terminal-style log window appears
3. Wait a few minutes for the process to complete
4. When done, a URL will be provided summarizing the repair details

This URL includes system logs and configuration details. If the repair doesn’t work, you can share this link on support forums to get help from the community.

Before You Reboot: Final Checks

Once Boot Repair finishes, it will tell you to reboot. But before restarting your system, make sure to check the following:

• Is the correct boot drive selected in the BIOS/UEFI settings?
• Are any external USB drives or storage devices still connected?
• If you dual-boot with another OS like Windows, will that OS still be accessible?

In UEFI environments, Boot Repair might create a new boot entry. That could change the boot order, so double-check your BIOS settings if needed.

How to Use the Boot Repair Log URL

After the repair, Boot Repair will display a URL that looks something like this:

https://paste.ubuntu.com/p/abcd1234/

This link contains detailed info about your system, GRUB configuration, and partitions. If the fix didn’t work, sharing this URL on Ubuntu forums or Q&A sites will make it easier for others to help you troubleshoot.

5. Manual GRUB Repair (When Boot Repair Doesn’t Work)

When Boot Repair Isn’t Enough

Boot Repair is a powerful tool, but it can’t solve every problem. In certain cases, you may need to repair GRUB manually, especially if:

• The EFI partition wasn’t mounted correctly
• GRUB misdetects the setup in a complex multi-boot environment
• Disk configuration has changed and GRUB can’t locate the OS
• Boot Repair itself crashes and won’t start

In such cases, reinstalling GRUB manually can help you restore boot functionality.

Reinstalling GRUB Manually with chroot (BIOS Mode)

Manual repair usually involves these steps: boot with a Live USB → mount the root file system → enter a chroot environment.

Step 1: Mount the root partition (replace /dev/sda1 with your actual Ubuntu root)

sudo mount /dev/sda1 /mnt
sudo mount --bind /dev /mnt/dev
sudo mount --bind /proc /mnt/proc
sudo mount --bind /sys /mnt/sys

Step 2: Enter the chroot environment

sudo chroot /mnt

Step 3: Reinstall GRUB

grub-install /dev/sda
update-grub

Step 4: Exit chroot and reboot

exit
sudo reboot

This process should rebuild GRUB and make Ubuntu bootable again.

For UEFI Systems: Additional Steps Required

For systems using UEFI, you’ll also need to mount the EFI partition (usually /boot/efi). Add this step before running grub-install inside chroot:

Mount the EFI partition (replace /dev/sda2 with your actual EFI partition)

sudo mount /dev/sda2 /mnt/boot/efi

Then inside the chroot environment, run:

grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=ubuntu
update-grub

Note: In UEFI mode, if Secure Boot is enabled in your BIOS, GRUB might fail to load. If you run into issues, try temporarily disabling Secure Boot.

Advanced Manual Repair Example (Optional)

If you have multiple operating systems installed, you can manually edit the GRUB configuration file (/etc/default/grub) to customize the boot order or menu display.

sudo nano /etc/default/grub

For example, to set the GRUB menu timeout to 10 seconds:

GRUB_TIMEOUT=10

After making changes, apply them with:

update-grub

6. Common Boot Issues: Case-by-Case Solutions

Ubuntu boot issues can vary depending on the user’s environment. This section introduces specific causes and fixes for common scenarios, using both Boot Repair and manual recovery methods as needed.

Case 1: Ubuntu Fails to Boot After a System Update

Symptoms:

• GRUB doesn’t show up after the update
• Black screen or “no bootloader found” error

Cause: Kernel updates or GRUB misconfiguration

Solution:

• Boot into a Live USB and run Boot Repair using “Recommended repair”
• If that fails, run update-grub manually in a chroot environment

sudo mount /dev/sda1 /mnt
sudo chroot /mnt
update-grub

Case 2: Dual Boot with Windows — Ubuntu Won’t Start

Symptoms:

• Only Windows boots
• GRUB is gone and the system boots directly into Windows Boot Manager

Cause: A major Windows update may have overwritten the GRUB bootloader

Solution:

• Use a Live USB to reinstall GRUB with Boot Repair

grub-install /dev/sda
update-grub

• After running Boot Repair, set the boot order to “Ubuntu” in BIOS/UEFI
• It’s also recommended to disable Fast Startup in Windows settings

Case 3: System Fails to Boot After Replacing or Adding SSD/HDD

Symptoms:

• GRUB appears, but no OS is found
• Error messages like “unknown filesystem” or “grub rescue”

Cause: Changing drives may alter UUIDs or device names, breaking GRUB’s configuration

Solution:

• Use a Live USB to mount the root partition and run update-grub
• Check and correct UUIDs in /etc/fstab if needed

blkid  # Check UUIDs
sudo nano /mnt/etc/fstab

Case 4: Boot Fails Due to Mismatch Between BIOS and UEFI Settings

Symptoms:

• GRUB was installed, but the system still won’t boot
• Errors like “No bootable device” or “Missing OS”

Cause: Ubuntu was installed in UEFI mode, but BIOS is now set to legacy mode (or vice versa)

Solution:

• Change BIOS settings to UEFI mode, then run Boot Repair to fix the EFI boot entry
• Advanced users can check/edit boot entries using efibootmgr

sudo efibootmgr -v

Case 5: GRUB Menu Doesn’t Show — Ubuntu Boots Directly

Symptoms:

• Ubuntu boots fine, but other OS (e.g., Windows) can’t be selected
• GRUB menu never appears at startup

Cause: GRUB menu is hidden by default in its configuration

Solution:

• Edit the GRUB config file to enable the menu

sudo nano /etc/default/grub
# Edit the following lines:
GRUB_TIMEOUT_STYLE=menu
GRUB_TIMEOUT=10

• After editing, apply changes with update-grub

7. FAQ: Frequently Asked Questions About Boot Repair and Ubuntu Boot Issues

Here are answers to common questions about Boot Repair and Ubuntu boot problems. Use this section as a quick reference to help you troubleshoot more effectively.

Q1. Do I need an internet connection to use Boot Repair?

A1.
It’s not required, but having an internet connection is highly recommended. Boot Repair can reinstall GRUB packages and upload system logs to a server, which is helpful for getting support. Without internet, basic repairs still work, but log sharing and updates are limited.

Q2. After using Boot Repair, I can’t boot into Windows. What should I do?

A2.
GRUB might not have detected Windows correctly. Try the following steps:

1. Boot from a Live USB
2. Open a terminal and run Boot Repair, choosing “Recommended repair”
3. If that doesn’t work, update GRUB manually via chroot

sudo mount /dev/sda1 /mnt
sudo chroot /mnt
update-grub

This should restore the Windows boot entry in the GRUB menu.

Q3. The GRUB menu doesn’t show up — Ubuntu boots directly. Why?

A3.
By default, GRUB may be set to hidden mode. To show the boot menu, edit the GRUB configuration:

sudo nano /etc/default/grub

Change the following lines:

GRUB_TIMEOUT_STYLE=menu
GRUB_TIMEOUT=10

Then apply the changes with:

sudo update-grub

Now, the GRUB menu should appear on boot.

Q4. After using Boot Repair, my screen stays black — what’s wrong?

A4.
The repair may have worked, but your display driver or startup config might be causing the blank screen. Try the following:

• In the GRUB menu, choose “Advanced options” and select a different kernel
• Press e at the GRUB menu and remove quiet splash to view detailed boot logs
• Try booting in recovery mode to diagnose driver issues

Q5. After using Boot Repair, my BIOS boot order changed. What should I do?

A5.
Boot Repair may have created a new boot entry, changing the boot priority. Open your BIOS/UEFI settings (usually by pressing DEL or F2 on startup) and make sure the “ubuntu” or “GRUB” entry is set as the first boot option.

Q6. I don’t understand the difference between UEFI and BIOS. Does Boot Repair work with both?

A6.
Yes, Boot Repair supports both UEFI and BIOS (Legacy) boot modes. However, it’s important to boot your Live USB in the same mode as your Ubuntu installation. If Ubuntu was installed in UEFI mode, Boot Repair must also run in UEFI mode to work correctly.

8. Conclusion: Don’t Fear Boot Issues — Boot Repair Makes Recovery Easy

Key Takeaways About Boot Repair

• Beginner-friendly GUI tool — you can repair GRUB with just a few clicks
• Works with Live USB — no need to reinstall Ubuntu, and minimal command-line use required
• If automatic repair fails, manual GRUB reinstallation can still fix most issues
• Handles both UEFI and BIOS setups, and works in dual-boot environments
• Provides practical tips, like using boot logs and rebuilding GRUB menus

How to Prepare for Future Boot Issues

To keep Ubuntu running smoothly, here are a few simple but effective precautions:

• Back up your system regularly (use tools like Timeshift)
• Create restore points before major updates
• Understand your BIOS/UEFI settings and document any changes
• Learn about Boot Repair in advance and keep a Live USB ready

Even simple preparation can give you peace of mind when something unexpected happens.

Boot Troubles = Learning Opportunities

GRUB errors and boot failures may seem intimidating at first — especially if you’re new to Linux. But solving these problems is a great way to deepen your understanding of Ubuntu and how your system works. Boot Repair is an excellent first step on that journey.

So the next time your system refuses to boot, don’t panic. Use this guide to walk through the process calmly and confidently. You’ll come out of it not just with a working system — but with more Linux knowledge under your belt.