Dual booting lets you run Windows and Linux on the same PC, choosing which one to use each time you start your computer. It is the ideal way to try Linux without giving up Windows — your files, applications and Windows installation remain untouched. This guide explains how to set up a dual boot with Windows 11 (or Windows 10) and Ubuntu.
What Is Dual Booting?
When you dual boot, both operating systems are installed on your hard drive in separate partitions. When you turn on your PC, a boot menu appears asking which operating system you want to start. You pick one and it loads normally — the other is not running at all.
Your Windows files and Linux files are stored separately and do not interfere with each other. You can access your Windows files from Linux, but Windows cannot access most Linux filesystems.
Before You Start
Back up your data. Partitioning a hard drive always carries some risk. Before proceeding, back up your important files to an external drive or cloud storage.
Check your drive has enough space. Ubuntu needs at least 25GB; realistically you want 50–100GB for a comfortable Linux install. You will need to shrink your Windows partition to make room.
Check your boot mode. Modern PCs use UEFI. Press Windows + R, type msinfo32, and look for BIOS Mode. If it says UEFI, you are in the right mode. This guide assumes UEFI mode.
Disable Fast Startup in Windows. Fast Startup can cause filesystem conflicts. Go to Control Panel > Power Options > Choose what the power buttons do > Turn on fast startup, and uncheck it.
Step 1 — Create Free Space for Linux
You need to create an unallocated partition on your hard drive for Linux. The easiest way is using Windows Disk Management:
- Right-click the Start button and select Disk Management
- Right-click your main Windows drive (usually C:) and select Shrink Volume
- Enter the amount to shrink in MB. For a comfortable Linux installation, shrink by at least 51200 MB (50GB). Type the number and click Shrink.
- A new black Unallocated block will appear in Disk Management — this is where Linux will be installed
Step 2 — Create a Bootable Ubuntu USB Drive
Download the Ubuntu ISO from ubuntu.com and write it to a USB drive using Rufus (free, download from rufus.ie):
- Open Rufus with your USB drive inserted
- Select your USB drive and choose the Ubuntu ISO file
- Leave other settings at defaults and click Start
- Choose ISO Image mode if prompted
- Wait for the process to complete
Step 3 — Boot from the USB Drive
- Restart your PC with the USB drive plugged in
- Press the boot menu key (usually F12, F2, or Esc) during startup
- Select the USB drive from the boot menu
- Ubuntu will load to a welcome screen
Step 4 — Install Ubuntu Alongside Windows
- Click Install Ubuntu on the welcome screen
- Choose your language and keyboard layout
- On the Updates and other software screen, select Normal installation and check both download and third-party software options
- On the Installation type screen, select Install Ubuntu alongside Windows Boot Manager
- If this option does not appear, select Something else and manually set up the partition (see below)
- Confirm the partition allocation. By default, Ubuntu will use the free/unallocated space you created in Step 1.
- Set your time zone, create a username and password, and click Install now
- Wait 10–20 minutes for installation to complete
- When prompted, remove the USB drive and click Restart now
Step 5 — The Boot Menu (GRUB)
When your PC restarts, you will see the GRUB boot menu — a text-based menu that lets you choose between Ubuntu and Windows. By default it highlights Ubuntu; press Enter to confirm, or use arrow keys to select Windows.
GRUB will appear every time you start your PC. If you do not press any key within a few seconds, it will automatically boot the highlighted option (usually Ubuntu).
Switching Between Operating Systems
To switch operating systems, simply restart your PC and choose the other option from the GRUB menu. Your files in one OS are not affected when you use the other.
From Linux, you can access Windows files: Your Windows drive (NTFS partition) is usually accessible from the Linux file manager under Devices. You can read and write Windows files from Linux.
From Windows, you cannot access Linux files: Windows does not natively read the Linux filesystem (ext4). There are third-party tools that can do this, but it is not built in.
Troubleshooting Common Issues
Windows does not appear in the GRUB menu
Run sudo update-grub in an Ubuntu terminal. GRUB should detect Windows and add it to the menu.
“Install Ubuntu alongside Windows” option does not appear
Ubuntu may not have detected your Windows installation if it is on a separate drive or in a non-standard configuration. Choose Something else to manually partition. Create a root partition (/) in the unallocated space using ext4 format.
Time is wrong in Windows after using Linux
Linux stores time as UTC in hardware clock; Windows stores local time. Fix this in Ubuntu by running: timedatectl set-local-rtc 1
