How to Dual Boot Ubuntu Linux Alongside Windows 11

Installing Ubuntu Linux alongside Windows 11 gives you the best of both worlds. You can keep Windows for applications that require it while using Ubuntu for development, privacy, or simply because you prefer it. This setup is called dual booting, and it lets you choose which operating system to start each time you turn on your computer.

This guide walks you through the entire process from start to finish, including preparing your Windows installation, creating a bootable Ubuntu USB drive, partitioning your hard drive, installing Ubuntu, and configuring the boot menu.

What You Need Before Starting

• A computer with Windows 11 already installed.
• A USB flash drive with at least 8 GB of storage (this will be erased during the process).
• At least 50 GB of free disk space for Ubuntu (more is recommended if you plan to store files on Ubuntu).
• A stable internet connection for downloading Ubuntu.
• A backup of your important Windows files (always recommended before modifying partitions).

Important: Back up your important data before proceeding. While dual booting is generally safe, modifying disk partitions always carries a small risk.

Step 1: Disable BitLocker Encryption (if Enabled)

Many Windows 11 computers have BitLocker drive encryption enabled by default. You need to suspend or disable BitLocker before installing Ubuntu, otherwise Ubuntu will not be able to access or modify the disk partitions.

1. Open the Start menu and search for BitLocker.
2. Click Manage BitLocker.
3. If BitLocker is enabled on your main drive, click Suspend protection or Turn off BitLocker.
4. Wait for the decryption process to complete.

You can re-enable BitLocker after the dual boot setup is complete if needed, though be aware that BitLocker may need special configuration to work correctly alongside a dual boot setup.

Step 2: Shrink the Windows Partition

You need to create free space on your hard drive for Ubuntu. The easiest way is to shrink the existing Windows partition from within Windows.

1. Right-click the Start button and select Disk Management.
2. Find your main Windows partition (usually the C: drive).
3. Right-click it and select Shrink Volume.
4. In the Enter the amount of space to shrink field, enter the amount of space you want for Ubuntu in megabytes. For example, 100,000 MB equals approximately 100 GB.
5. Click Shrink.

After shrinking, you will see a block of Unallocated space in Disk Management. Do not format or assign a drive letter to this space. The Ubuntu installer will use it during installation.

Recommended partition sizes for Ubuntu:

Use Case	Minimum Space	Recommended Space
Basic Ubuntu with light use	25 GB	50 GB
Ubuntu with applications and files	50 GB	100 GB
Ubuntu as a primary development OS	100 GB	200 GB+

Step 3: Download Ubuntu

1. Go to the official Ubuntu download page at ubuntu.com/download/desktop.
2. Download the latest LTS (Long Term Support) version. LTS versions receive security updates for five years, making them the best choice for most users.
3. The download is an ISO file, approximately 5 GB in size.

Step 4: Create a Bootable USB Drive

You need to write the Ubuntu ISO file to a USB drive so you can boot from it.

Using Rufus (Recommended for Windows)

1. Download Rufus (a free, lightweight tool for creating bootable USB drives).
2. Insert your USB drive into your computer.
3. Open Rufus.
4. Under Device, select your USB drive.
5. Under Boot selection, click SELECT and choose the Ubuntu ISO file you downloaded.
6. Leave all other settings at their defaults (Rufus will automatically configure the correct settings for Ubuntu).
7. Click START.
8. If prompted about ISO vs DD mode, select ISO mode (the recommended option).
9. Wait for the process to complete. This usually takes a few minutes.

Warning: Creating a bootable USB drive erases everything on the USB drive. Make sure you have backed up any important files.

Step 5: Boot from the USB Drive

1. Restart your computer with the USB drive inserted.
2. As the computer restarts, press the boot menu key. This varies by manufacturer:
   • Dell: F12
   • HP: F9 or Esc
   • Lenovo: F12 or Fn + F12
   • ASUS: F2 or Esc
   • Acer: F12
3. From the boot menu, select your USB drive.
4. If asked, select Try or Install Ubuntu.

If your computer boots directly into Windows instead of showing the boot menu, you may need to disable Secure Boot or Fast Boot in your BIOS/UEFI settings. You can access BIOS/UEFI by going to Settings → System → Recovery → Advanced startup → Restart now, then selecting Troubleshoot → UEFI Firmware Settings.

Step 6: Install Ubuntu Alongside Windows

Once Ubuntu boots from the USB drive:

1. Select your language and click Install Ubuntu.
2. Choose your keyboard layout.
3. Connect to Wi-Fi if available (optional but recommended for downloading updates during installation).
4. Choose Normal installation (includes a web browser, office tools, and media players).
5. Tick Download updates while installing Ubuntu for the latest security patches.
6. Tick Install third-party software for graphics and Wi-Fi hardware for better hardware compatibility.
7. On the installation type screen, select Install Ubuntu alongside Windows Boot Manager. This is the safest option and automatically handles partitioning.
8. Use the slider to adjust how much space to give Ubuntu versus Windows, or accept the default split.
9. Click Install Now.
10. Confirm the partition changes when prompted.
11. Select your time zone.
12. Create your Ubuntu username and password.
13. Wait for the installation to complete.

When the installation finishes, click Restart Now and remove the USB drive when prompted.

Step 7: Choose Your Operating System at Startup

After restarting, you will see the GRUB boot menu. This menu appears every time you start your computer and lets you choose between:

• Ubuntu — Boots into Ubuntu Linux.
• Windows Boot Manager — Boots into Windows 11.

Use the arrow keys to select your choice and press Enter. If you do not make a selection, Ubuntu boots by default after a few seconds.

How to Change the Default Boot Operating System

If you want Windows to be the default boot option instead of Ubuntu:

1. Boot into Ubuntu.
2. Open a terminal (press Ctrl + Alt + T).
3. Edit the GRUB configuration file:

sudo nano /etc/default/grub

Find the line:

GRUB_DEFAULT=0

Change it to match the position of Windows in the boot menu (usually 2 or the number next to the Windows Boot Manager entry). Alternatively, use:

GRUB_DEFAULT=saved
GRUB_SAVEDEFAULT=true

This tells GRUB to remember the last operating system you booted and default to it next time.

Save the file (Ctrl + O, then Enter, then Ctrl + X) and update GRUB:

sudo update-grub

Troubleshooting Common Dual Boot Issues

Windows and Ubuntu Show the Wrong Time

Windows and Linux handle hardware clocks differently. Windows uses local time by default, while Ubuntu uses UTC. This can cause the time to be incorrect in one OS after using the other.

The simplest fix is to tell Ubuntu to use local time for the hardware clock:

timedatectl set-local-rtc 1 --adjust-system-clock

GRUB Boot Menu Does Not Appear

If your computer boots directly into Windows without showing the GRUB menu, Windows may have overwritten the boot order. You can fix this by:

1. Booting from the Ubuntu USB drive again.
2. Selecting Try Ubuntu (without installing).
3. Opening a terminal and running Boot Repair:

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

Follow the on-screen instructions to repair GRUB.

Windows Update Breaks GRUB

Major Windows updates can sometimes overwrite the GRUB bootloader. If this happens, use the same Boot Repair process described above to restore the dual boot menu.

How to Remove Ubuntu from a Dual Boot Setup

If you decide you no longer want Ubuntu:

1. Boot into Windows.
2. Open Disk Management.
3. Delete the Ubuntu partitions (they will appear as unrecognised or without a drive letter).
4. Extend your Windows partition to reclaim the freed space.
5. Open an elevated Command Prompt and run bootrec /fixmbr to remove GRUB and restore the Windows bootloader.

Dual booting Ubuntu alongside Windows 11 is a reliable way to use both operating systems on the same computer. The Ubuntu installer handles most of the complexity automatically, and the GRUB boot menu makes it easy to switch between them whenever you start your computer.