How to Fix Windows and Linux Dual Boot Not Showing Boot Manager

If your computer boots directly into Ubuntu without showing the boot manager, you may be facing an issue with GRUB (GNU GRUB bootloader) or BIOS/UEFI settings. This guide will help you troubleshoot and fix the problem so that you can choose between Windows and Linux when you start your computer.

Common Causes of Missing Boot Manager

• Fast Boot or Secure Boot is enabled in BIOS/UEFI
• Windows Boot Manager is not detected by GRUB
• GRUB is not properly installed or configured
• Incorrect boot order in BIOS/UEFI settings

Step-by-Step Solutions

1. Check Boot Menu Access

Before making changes, try accessing the boot menu manually:

1. Restart your computer.
2. Press the appropriate key for your system to open the boot menu (Esc, F12, F2, F10, or Del depending on your manufacturer).
3. If Windows Boot Manager is listed, select it to boot into Windows.
4. If it’s missing, proceed with the next steps.

2. Modify GRUB Settings to Show Boot Menu

By default, Ubuntu may hide the boot menu. To change this:

1. Boot into Ubuntu.
2. Open a terminal and run:

sudo nano /etc/default/grub

1. Find the following lines and modify them:

GRUB_TIMEOUT_STYLE=hidden  # Change "hidden" to "menu" 
GRUB_TIMEOUT=0  # Change 0 to 5 (or more)

1. Save the file (Ctrl + X, then Y, then Enter).
2. Update GRUB:

sudo update-grub

1. Restart your computer to see if the boot menu appears.

3. Detect Windows Boot Manager

If Windows is missing from the GRUB menu:

1. Boot into Ubuntu.
2. Open a terminal and run:

sudo os-prober 
sudo update-grub

1. Restart your computer and check if Windows appears in the boot menu.

4. Reinstall GRUB Bootloader

If GRUB is corrupted, reinstall it:

1. Boot into Ubuntu.
2. Open a terminal and run:

sudo grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=GRUB 
sudo update-grub

1. Restart your computer.

5. Check BIOS/UEFI Settings

If Windows still doesn’t appear:

1. Restart and enter BIOS/UEFI (Press F2, F10, F12, or Del at startup).
2. Disable Fast Boot and Secure Boot.
3. Ensure that the boot order prioritizes GRUB.
4. Save changes and restart.

Final Thoughts

Following these steps, you can easily restore the boot manager and switch between Windows and Linux. If the issue persists, consider using Boot Repair by running Ubuntu in a live session and installing the boot-repair tool:

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

After running Boot Repair, restart and check if the boot menu appears. Let us know if you need further assistance!