Windows: how to prepare it for dual boot with Linux Mint or Ubuntu

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Do you want to install Linux Mint or Ubuntu next to Windows, in order to create a dual boot computer? Then first you have to change some settings in Windows, and when you have a pre-installed Windows 10 or 11, also in the BIOS ("UEFI") of your computer. As follows:

Contents of this page:

Disable Fast Startup (no loss, it's misleading anyway)

1. In Windows 10 and 11, you first have to disable Fast Startup. Fast Startup is essentially an advanced hibernation: shutdown doesn't really shut your computer down, but puts it in a sleep condition.

By disabling Fast Startup a shutdown becomes a real shutdown again, which makes the Windows partition on your hard disk, accessible and resizable by Ubuntu or Linux Mint.

Disable Fast Startup like this:

a. Control Panel - Power Options - Choose what the power buttons do

b. Now click on Change settings that are currently unavailable. See the screenshot below:

c. Now remove the tick for Turn on fast startup (recommended), even though this bothersome feature is supposedly "recommended". See the screenshot below:

d. Click on Save changes.

e. Reboot your computer. Don't shut it down! It has to be a reboot, in order to make this settings change permanent.

If you have an old computer which was originally sold with a pre-installed Windows 7, Vista or XP (which means old-fashioned BIOS): you're done! You can continue with the actual installation of Linux Mint.

But if your computer was sold with a pre-installed Windows 8, 10 or 11 (which means modern UEFI), please read on.

Disable BitLocker (if you have it)

2. Some Windows machines are encrypted with BitLocker. That's a problem, because BitLocker can block a successful dual boot installation of Linux Mint.

So disable it in Windows before you start. Probably (I haven't tested this) you can enable BitLocker again after the dual boot installation of Linux Mint has completed.

Change some BIOS settings

3. If you have a modern computer that was sold with a pre-installed Windows 8, 10 or 11, you now need to open the configuration of your BIOS (UEFI). If you don't know how to do that, see the manual of your computer. Don't you have the manual anymore? You should always be able to find a copy in the support section of the website of the manufacturer.

For an Acer, you have to press the F2 key a couple of times, directly after turning on the computer.

Can't you succeed in accessing the BIOS (UEFI) configuration? Then you can also evoke it from within Windows 10 or 11, in an annoyingly cumbersome way:

Click on the magnifier icon in the panel of Windows 10 or 11 - let it search your system ("Type here to search") with the term settings
Click on the first (preselected) result, namely the app Settings

Then scroll down in the Settings window and select: Recovery - Advanced Startup: click on Restart now

Then: Troubleshoot - Advanced options - UEFI Firmware Settings: click on Restart

Finally, at very long last (sigh....) you should be able to access the UEFI configuration.

Disable Secure Boot

3.1. Now disable Secure Boot in the BIOS. For Ubuntu this is often no longer necessary, because Ubuntu (unlike Linux Mint) contains a digital signature for Secure Boot. However, sometimes it still causes problems even for Ubuntu. So when your BIOS allows for it, I advise to disable Secure Boot in all cases.

No worries: although Secure Boot is a fairly reasonable idea in theory, it provides little real-life security anyway. So disabling it is no loss. In practice, Secure Boot is primarily an obstacle for using another operating system than Microsoft Windows. Which might or might not be an intended side effect.

Note: in some cases, you need to set an administrator password in the BIOS before you can disable Secure Boot.

See the screenshot below, of the BIOS of an Acer TravelMate laptop (click on the picture to enlarge it):

Put Windows Boot Manager at the bottom of the boot priority order

3.2. Then you put the Windows Boot Manager permanently at the bottom of the boot priority order. Sometimes it's hidden in something called OS Boot Manager (OS = Operating System), in which case you'll have a job to do after installing Linux: you'll need to expand OS Boot Manager and put Windows Boot Manager at the bottom of the list within the OS Boot Manager section.

See the screenshot below of the BIOS of an Acer Travelmate laptop (click on it to enlarge it):

If possible: enable the key for one-time boot priority changes

3.3. Finally, enable the key for temporary one-time changes in the boot priority order (if your BIOS has that option in its settings). For an Acer that's usually F12, but this varies among manufacturers). See the screenshot below (click on it to enlarge it):

Save and exit.

Sometimes necessary: enable CSM (in some cases: Legacy)

3.4. In some cases it's necessary to enable CSM (Compatibility Support Module). In some cases this is called "Legacy". This provides legacy BIOS compatibility, by emulating an old-fashioned BIOS environment.

You should find this option in each BIOS, usually in the Boot section. ASUS calls it "Launch CSM".

First try it without CSM, because in a few cases CSM creates problems of its own. So only do this when necessary.

In case of emergencies: perform a one-time boot priority change

4. Note: after installation of Mint, Windows might not appear in the Grub bootloader menu. Or the boot entry for Windows in the Grub menu, might not work.

In those cases, you can still boot Windows by using the key for one-time changes in the boot priority order (for Acer: F12). That way, you bypass Grub entirely and you can boot Windows directly from the BIOS.

In that one-time BIOS boot menu, select Windows Boot manager. See the screenshot below of an Acer laptop (click on the picture to enlarge it):

Now Windows should boot normally.

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