[multi-boot] Manjaro and Windows (Separate Disks)

soundofthunder · 7 March 2024 06:44

Multi-boot Manjaro and Windows
…on Separate Disks

Firstly, this guide is intended for multi-booting with each OS on a separate disk.

If you have a laptop with only one disk, or If you wish to install an OS on it’s own partition on the same disk, this guide is not for you (but read on regardless, if interested).

Secondly, this guide assumes each OS will be installed using UEFI and not UEFI’s CSM or Legacy mode. This guide does not support the traditional BIOS boot method. Additionally, all disks must use the GPT partitioning scheme.

Knowledge and some understanding of these terminologies is assumed. Without that, you will have additional reading to undertake before setting up a multi-boot system. To that end, an Internet search can be your friend; and, this will get you started:

What Is UEFI, and How Is It Different from BIOS?

When creating a multi-boot scenario, each OS needs to be protected from the affects of installing another OS (no matter which is already installed). It is therefore recommended to first disconnect the disk containing an existing OS before installing a second; or a third.

The General Guide

First, disconnect any previous OS disk(s). Install the new OS (in UEFI mode) to a new disk, and when fully functional, reconnect the original OS disk. Set the Linux OS first in boot order, solve any temporary Grub issues; and install rEFInd (optional) for good measure.

STEP BY STEP

Note:- This procedure makes no assumption of which OS (Linux/Windows) is installed first.

Shutdown, turn off, and unplug your computer.
Disconnect any existing OS disk(s).
Plug in the power again.
Boot with the respective OS Installer (DVD/USB).
Install the new OS to the new disk and configure the OS.
Shutdown, turn off, and unplug your computer.
Reconnect the previous OS disk.
Plug in the power again.
Boot to your BIOS and select Manjaro as the first boot option.
Reboot, and enjoy.

Important Caveats

SECURE BOOT

Manjaro does not support a Secure Boot configuration. As every BIOS is different, the procedure to disable Secure Boot may also be different; consult your BIOS documentation for any required information.

If Secure Boot is enabled due to a Microsoft requirement (Windows 11), a workaround may need to be employed to allow Windows to boot without Secure Boot.

windows 11 bypass secure boot requirement

Secure Boot should be disabled before installing Manjaro.

SET MANJARO FIRST IN BOOT ORDER

Boot straight to BIOS settings and make sure the drive with Linux/Grub/rEFInd (your main EFI) is selected to boot first. Then reboot into Grub (or rEFInd).

WINDOWS FAST STARTUP

By default, Windows 10/11 use a hibernation variant that Microsoft calls Fast Startup – Windows doesn’t actually shut down, but instead wakes from hibernation giving the illusion of a faster startup; this frequently causes havoc with boot and NTFS mounting functionality within Linux.

Fast Startup must be disabled in a multi-boot scenario.

Disable Fast Startup using the following command from an administrative command prompt in Windows:

powercfg /h off

FAST BOOT

Fast Boot is a BIOS option which, if present, allows to skip certain self-tests during pre-boot (before handoff to a boot loader). As every BIOS is different, Fast Boot settings may exist in varying locations, or may not exist at all.

If Fast Boot is enabled, it is generally recommended (but not compulsory) to disable it in your BIOS when using Linux.

UTC VS. LOCAL TIME

Linux defaults to using UTC time rather than Local time; Windows uses Local time.

This causes particular annoyance when multi-booting, as each OS defaults to a different time standard and sets the BIOS clock accordingly on each boot. No matter how many times you might manually set the correct time (in either OS), it always resets after a reboot.

Methods exist to resolve this in Linux, however this author has found those to be unreliable. This issue only exists due to a Windows design flaw, or oversight; so, let Windows in turn assume the burden of repair. Linux already handles UTC with superior grace.

The most elegant solution is to create a Windows registry file with the following content;

Let’s call it RealTimeIsUniversal.reg:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation]
"RealTimeIsUniversal"=dword:00000001

After merging this registry modification, Windows will be ready to set the BIOS time to UTC after the next reboot. Windows time will need to be manually set once after the reboot, but from that point forward, both Windows and Linux will use the UTC time standard.

Note that this modification will not affect your date/time display in Windows. Configure it as you would normally.

WINDOWS MISSING FROM GRUB MENU

Windows may not (yet) appear in the GRUB menu;- this might be expected with a new multi-boot configuration.

The package os-prober is responsible for detecting other Operating Systems during boot. If you wish to rely on Grub to manage booting each OS then it is imperative that os-prober is enabled.

OS-Prober is now enabled by default in Manjaro¹.

→ 1. Official Manjaro editions.

OS-Prober (How to enable)

Verify that os-prober is installed; install it, if it isn’t:

# Verify os-prober is installed
pacman -Qi os-prober
# Install os-prober (if needed)
sudo pacman -S os-prober

In order for os-prober to detect another available OS during boot, it needs to be enabled in /etc/default/grub, which right now, it probably isn’t.

Check os-prober status;

# Check the status of os-prober:
cat /etc/default/grub | grep -i 'OS_PROBER'
# The output will include this line:
GRUB_DISABLE_OS_PROBER=false

If the line is commented (#), uncomment it:

# Edit `/etc/default/grub`:
sudo nano /etc/default/grub

# The line should look exactly like:
GRUB_DISABLE_OS_PROBER=false

# Update GRUB:
sudo update-grub

On next reboot, os-prober should function as expected, and Windows (or any other properly installed OS) should be automatically detected and listed in the GRUB menu.

OS-Prober (A security perspective):

The following information remains only for interest sake:

Due to a security recommendation (since GRUB v2.06) os-prober is/was disabled by default on Arch Linux based systems; in some cases, removed completely.

Is this something to be concerned about? This author thinks not, especially not, if you trust those around you who might sit in your chair.

While there is/was a valid security reason for this decision, it is incredibly inconvenient to not have os-prober enabled if you’re depending on Grub for multi-booting.

rEFInd UEFI Boot Manager

The rEFInd UEFI Boot Manager is a versatile and more manageable solution to multi-booting with several Linux flavours in the mix.

Having each OS on a separate disk (with its own $ESP) is an ideal scenario for multi-booting.

rEFInd assumes the role of the initial boot loader, which in turn effectively chain-loads other UEFI boot loaders, including the GRUB efi-stub, the Windows boot loader (or even MacOS and BSD).

This allows one to leave each GRUB untouched and managed by it’s respective OS – this means less maintenance (no juggling settings to enable a successful boot) – plus, the added convenience of being able to bypass any installed GRUB and boot the respective kernel-stub directly.

This is exceptionally handy if GRUB has failed to boot, as you can still boot into Manjaro and repair it in relative comfort.

Installing rEFInd on a Manjaro/Windows multiboot system should give these boot choices by default (the naming may differ, but this gives the general idea):

Windows
Manjaro (GRUB efi-stub)
Manjaro (kernel-stub)

The easiest way to see rEFInd in action is to install it (available from the official Manjaro repos):

Setting up refind is quite easy;

1. Install the refind package so that it’s available to Manjaro.

sudo pacman -S refind

2. Use refind’s own tool to install it to the $ESP.

sudo refind-install

rEFInd will be copied to it’s own folder on the Manjaro $ESP; the directory layout will be similar to:

EFI
├─ BOOT
├─ Manjaro
└─ refind

See also: The rEFInd Boot Manager: Methods of Booting Linux.

BOOT PRIORITY ‘HIJACKING’

Some Linux distributions (such as Debian) cause the boot priority to be reset after every update causing a “boot coup”.

If you are multi-booting with other Linux flavours in the mix, it might be beneficial to move the rEFInd boot files to the default/fallback location $ESP /EFI/BOOT to ensure it isn’t affected.

rEFInd provides a way to do this.

1. Identify your disk device node and partition number of your $ESP

lsblk -b

Look for the ESP on the same disk that contains Manjaro.

2. Move rEFInd files to the fallback location (/EFI/BOOT)

Note the syntax differences between disk types

For SATA/HDD:

sudo refind-install --usedefault /dev/sdXY

Substitute X and Y for your $ESP:

X is the disk node
Y is the partition number

For NVME:

sudo refind-install --usedefault /dev/nvmeXnYpZ

Substitute X, Y and Z for your $ESP:

X is the NVMe controller
Y is the disk node
Z is the partition number

3. Reboot