How to Troubleshoot Ubuntu Not Booting

Edited 3 weeks ago by ExtremeHow Editorial Team

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Ubuntu, a popular Linux distribution, is known for its robustness and reliability. However, sometimes users may encounter problems where Ubuntu fails to boot. This can be a frustrating experience, but understanding the possible causes and solutions can help you effectively troubleshoot and resolve the issue. This guide will outline several ways to troubleshoot Ubuntu not booting, using simple and clear language to make it accessible even to individuals who may not be very technically inclined.

1. Understanding the boot process

Before moving on to troubleshooting, it is beneficial to have a basic understanding of the Ubuntu boot process. When you turn on your computer, the following sequence usually occurs:

1. The BIOS/UEFI initializes the hardware and hands over control to the bootloader.
2. The GRUB bootloader is responsible for loading the Ubuntu kernel.
3. The kernel initializes the rest of the system, and control is handed off to the initialization system (often systemd).
4. The init system starts necessary services and sets up the user environment.

2. Preliminary investigation

Before applying more technical solutions, start by performing some basic checks that may uncover or even resolve the boot problem:

2.1 Make sure your computer is getting power

It may seem simple, but make sure your computer is turned on and properly connected to the power source. Sometimes power problems can masquerade as boot problems.

2.2 Check hardware connections

If you recently opened your computer, double-check that all internal components such as RAM, hard drives, and other connections are secure. Loose connections can prevent your system from booting properly.

2.3 Check the connected peripherals

Disconnect any non-essential peripherals like USB drives and external hard disks. Sometimes these devices can interfere with the boot process.

3. Troubleshoot GRUB problems

3.1 Accessing the GRUB menu

If Ubuntu won't boot, the problem may be in GRUB (GRand Unified Bootloader). To access the GRUB menu:

• Restart your computer.
• Immediately press Esc key (or Shift for older systems) a few times to access the GRUB menu.

Once you're here, there are several things you can try:

3.2 Boot into Recovery Mode

In the GRUB menu, select Recovery Mode. This is often the second entry and follows the main Ubuntu boot option. This will allow you to boot into a limited environment where you can perform some maintenance:

1. Select “Resume” to boot normally.
2. Select “root” to access a root shell with minimal services loaded. Here, you can run commands to diagnose or repair your system. For example, you could run:

sudo fsck /dev/sda1

This will check and fix any file system errors on your primary partition (replace /dev/sda1 with your actual partition if different).

4. Repairing corrupted GRUB

If GRUB itself is corrupted, you'll need to repair it. You can do this as follows:

4.1 Using Live USB

If you are unable to boot in any mode, use an Ubuntu live USB:

1. Create a Ubuntu Live USB from another computer.
2. Boot from this USB by selecting it in your BIOS/UEFI boot menu.
3. Select “Try Ubuntu” to access the live session.

Once you are in the live session, open the terminal and do the following:

4.2 Reinstalling GRUB

Assume /dev/sda is your drive, replace it with the correct partition if necessary:

sudo mount /dev/sda1 /mnt
sudo mount --bind /dev /mnt/dev
sudo mount --bind /proc /mnt/proc
sudo mount --bind /sys /mnt/sys
sudo chroot /mnt
grub-install /dev/sda
update-grub
exit
sudo umount /mnt/dev
sudo umount /mnt/proc
sudo umount /mnt/sys
sudo umount /mnt

Try a reboot afterward to see if the issue is resolved.

5. Checking for file system issues

File system errors can also prevent the system from booting:

5.1 Using fsck

If you suspect a file system problem, you can use the fsck tool:

1. Boot into recovery mode or use a live USB.
2. Run the following command, replacing /dev/sda1 with your partition:

sudo fsck -f /dev/sda1

Follow the prompts to fix any reported issues.

6. Repair broken packages

Sometimes, upgrades or installations can result in broken packages that prevent booting:

6.1 Using dpkg

In recovery mode, select "dpkg" from the menu. This will attempt to fix any broken packages.

7. Reviewing the boot log

The boot log may give some idea of what's going wrong:

7.1 Viewing the System Log

In recovery mode or a terminal session, check for the following types of logs:

less /var/log/syslog
less /var/log/dmesg

Look for errors that might indicate what's wrong.

8. Checking for hardware problems

If you've tried software solutions to no avail, a hardware problem may be the cause:

8.1 RAM related problems

Faulty RAM can cause random boot problems. Run a memory test:

1. Access the GRUB menu.
2. Select "memtest" (if available) to check for errors.

8.2 Hard drive problems

Hard drive failure can also cause boot problems. If you suspect the disk is damaged, consider replacing it.

9. Updating the BIOS/UEFI

Outdated firmware can sometimes cause conflicts with system boot processes.

9.1 Updating the Firmware

Check your manufacturer's website for BIOS/UEFI updates.

10. Reinstalling Ubuntu as a last resort

If other methods fail, you may have to reinstall Ubuntu. This should be the last resort and make sure to backup the data before proceeding.

10.1 Performing a New Installation

Use the live USB to install Ubuntu afresh, choosing the option to overwrite the existing installation.

In conclusion, troubleshooting an Ubuntu system that won't boot involves a systematic approach: checking hardware, addressing GRUB issues, repairing the file system, reviewing logs, and considering reinstalling or updating software. With patience and these strategies, you should be able to diagnose and resolve almost all booting problems.

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