Dual-Boot Linux Alongside Windows 11 (2026)
Install Ubuntu next to Windows 11 safely with this dual-boot guide, including the BitLocker and Fast Startup steps that prevent data loss.
Dual-booting lets you keep Windows 11 for the software that needs it while running Linux for development, privacy, or simply to learn. Done carefully, you pick which system to boot every time you power on, with both installed side by side. Done carelessly, you can corrupt the Windows partition and lose data. The difference is almost always two settings that most tutorials skip: BitLocker and Fast Startup.
Quick answer
To dual-boot safely, back up your files, then disable BitLocker and Fast Startup in Windows, shrink the Windows partition in Disk Management to free 50 GB or more, write the Ubuntu ISO to a USB stick, and run the installer's Install Ubuntu alongside Windows Boot Manager option. Leave Secure Boot on. The whole process takes about 45 to 60 minutes, and you choose your operating system from a menu at every boot.
Key takeaways
- Back up your data first; partitioning always carries some risk.
- Disable BitLocker so Linux can resize the Windows partition.
- Turn off Fast Startup to avoid filesystem corruption.
- Modern Ubuntu (22.04 and later) works with Secure Boot left on.
- The installer offers an Install alongside Windows option that handles partitioning for you.
Prepare Windows first
Three preparation steps prevent the most common disasters. Skip any one of them and you are gambling with the Windows partition, so treat this as the part of the guide that actually matters.
- Back up everything important. A full disk image (Macrium Reflect or the built-in system image tool) plus a copy of key files to external storage is non-negotiable. Partitioning rewrites the disk's layout, and if the power drops mid-resize, a backup is the only thing standing between you and a reinstall.
- Disable BitLocker. Search for "Manage BitLocker" and turn it off for the system drive, then wait for it to finish decrypting before you continue. Encrypted partitions block the resize, and a half-decrypted drive is worse than either state. On many Windows 11 machines BitLocker is on by default even if you never set it up, so check rather than assume.
- Disable Fast Startup. In Control Panel, under Power Options then "Choose what the power buttons do," uncheck Fast Startup. Otherwise Windows leaves the disk in a hibernated state, and if Linux mounts that partition it can corrupt the filesystem the next time Windows resumes.
Here is why each step matters and what happens if you ignore it:
| Prep step | Why it matters | Risk if you skip it |
|---|---|---|
| Back up your data | Partitioning rewrites the disk layout | Total data loss if the resize fails |
| Disable BitLocker | Encryption locks the partition | Installer cannot shrink Windows; resize fails |
| Disable Fast Startup | Windows hibernates the disk | Corrupted Windows filesystem on next boot |
| Confirm UEFI mode | Ubuntu and Windows must boot the same way | GRUB menu never appears; boots straight to one OS |
Also check you are on UEFI: press Windows+R, run msinfo32, and confirm "BIOS Mode" reads UEFI. If it says Legacy or BIOS, installing Ubuntu in UEFI mode will hide the boot menu, so the two systems must match.
Make a bootable USB and free up space
Download the Ubuntu ISO from ubuntu.com and write it to a USB stick (8 GB or larger) with a tool like Rufus or balenaEtcher. Verify the download's checksum if you want to be thorough; a corrupted ISO is a common cause of installer crashes that people blame on hardware.
Then, in Windows, free up room: open Disk Management, right-click the Windows partition, and choose Shrink Volume to carve out unallocated space for Linux. Do the shrink from Windows rather than letting the Ubuntu installer do it, because Windows understands its own filesystem and is less likely to leave it inconsistent.
How much space you give Linux depends on what you plan to do with it:
| Use case | Space to allocate | Notes |
|---|---|---|
| Trying Linux out | 30-50 GB | Enough for the OS and light use |
| Daily driver | 80-120 GB | Room for apps, updates, and files |
| Development / VMs | 150 GB or more | Containers and toolchains eat space fast |
Leave Windows at least 60 GB of free space after the shrink so it can still install updates and operate normally.
Install Ubuntu alongside Windows
- Boot from the USB stick (use your PC's boot menu, often F12 or Esc).
- Choose Try or Install Ubuntu and run the installer.
- At the installation type screen, select Install Ubuntu alongside Windows Boot Manager.
- Adjust the slider to set how much space Linux gets, then continue.
- Finish the setup, remove the USB when prompted, and reboot.
On reboot you will see the GRUB menu letting you pick Ubuntu or Windows each time.
Warning
If the installer does not detect Windows, stop. Do not proceed with manual partitioning unless you are confident, since selecting the wrong option can erase Windows. Re-check that Fast Startup and BitLocker are off and try again.
After installation
On reboot you should land on the GRUB menu. From here, a few things commonly need attention, and most are quick fixes rather than disasters:
| Symptom | Likely cause | Fix |
|---|---|---|
| Boots straight to Windows | Firmware reordered boot entries | Move "Ubuntu" above "Windows Boot Manager" in UEFI |
| Clock is wrong in Windows | Linux uses UTC for the hardware clock | Set Linux to local time, or set Windows to UTC |
| No Wi-Fi in Ubuntu | Proprietary driver not loaded | Install the recommended driver in "Additional Drivers" |
| GRUB menu flashes too fast | Default timeout is short | Raise GRUB_TIMEOUT in /etc/default/grub |
If the machine boots straight into Windows and skips the menu, the firmware reordered the boot entries. Enter the UEFI settings and move "Ubuntu" above "Windows Boot Manager," or use the one-time boot menu to pick Ubuntu and confirm GRUB appears. The clock mismatch is the other near-universal annoyance: Windows and Linux disagree about whether the hardware clock is local time or UTC, so one of them shows the wrong time until you make them agree.
What to do right now
If you are about to start, run this checklist in order and do not skip ahead:
- Back up your files and, ideally, take a full system image.
- Turn off BitLocker and wait for decryption to finish.
- Uncheck Fast Startup in Power Options.
- Confirm
msinfo32shows UEFI mode. - Shrink the Windows partition to free at least 50 GB.
- Write the Ubuntu ISO to a USB stick and boot from it.
- Choose Install Ubuntu alongside Windows Boot Manager, not manual partitioning.
If you would rather avoid partitioning entirely, our guide to running Linux apps on a Chromebook shows a contained alternative, and if Windows itself becomes unbootable during this process, see fixing the Inaccessible Boot Device BSOD.
Frequently asked questions
Will dual-booting delete my Windows files?
Not if you use the "Install alongside Windows" option and prepared correctly. The risk comes from skipping BitLocker and Fast Startup steps or choosing manual partitioning by mistake. Back up first regardless.
Do I need to disable Secure Boot?
No. Ubuntu has supported Secure Boot natively since 22.04, so you can leave it enabled. Older guides telling you to disable it are out of date.
Why does my PC boot straight into Windows now?
The firmware reordered the boot entries. Enter UEFI settings and put the Ubuntu or GRUB entry first, or pick it from the one-time boot menu to confirm the menu still works.
How much disk space should I give Linux?
At least 50 GB is comfortable for the system plus apps and files. You can shrink the Windows partition to make room, leaving Windows enough space to keep operating normally.
