After installing Ubuntu 22.10 today in my desktop PC, the dual-boot Windows 10 disappeared from the startup boot menu. If you run into similar issue, here’s the quick tip to fix it.

This is definitely not bug, but a policy change since GNU Grub 2.06. The default boot-loader uses external os-prober tool to discover other operating systems on the same machine. However, the feature is disabled now for security reason due to the manual:

It is disabled by default since automatic and silent execution of os-prober, and creating boot entries based on that data, is a potential attack vector. Set this option to ‘false’ to enable this feature in the grub-mkconfig command.

By reloading the config will prompt your that “Warning: os-prober will not be executed to detect other bootable pertitions“.

Ubuntu 22.04 is the first release uses GRUB 2.06, which however not affected in my case. So I didn’t encounter this issue until trying Ubuntu 22.10 today on dual-boot machine. And, here’s how to fix the the ‘issue’ in 2 ways.

Option 1: Manually re-enable OS-PROBER

As mentioned in the manual, just set the ‘GRUB_DISABLE_OS_PROBER’ option to ‘false’ in Grub configuration will do the trick.

1. First, press Ctrl+Alt+T on keyboard to open a terminal window. When it opens, run command to edit the Grub config file:

sudo nano /etc/default/grub

Ubuntu 22.10 switched to gnome-text-editor which however does not work along-with sudo from command line. So here I use nano command line text editor instead.

2. When the file opens in terminal window, scroll down and add the new line (or change the value if the line already exists):

GRUB_DISABLE_OS_PROBER=false

After that, save changes by pressing Ctrl+X, type y and hit Enter.

3. Finally, run sudo update-grub to reload the change.

Don’t know why, but Windows OS appears in boot-menu again after I did restart computer twice in my case.

Option 2: Use Grub-Customizer (graphical tool)

For those who prefer using a graphical configuration tool, there’s a third-party Grub-Customizer app available for choice.

1. First, you still need to open terminal (Ctrl+Alt+T) and run 3 commands one by one to install the tool from developer’s PPA:

sudo add-apt-repository ppa:danielrichter2007/grub-customizer

sudo apt update

sudo apt install grub-customizer

2. Search for and launch grub customizer from system start menu or ‘Activities’ overview.

3. When the app opens, navigate to ‘General Settings‘ page, then do:

• click on bottom right advanced settings option.
• in next pop-up dialog, click “Add” (or edit if exists) and type:
  • name: GRUB_DISABLE_OS_PROBER
  • value: false

Close advanced settings dialog, and finally click “Save” button in the app to apply change.

This simple tutorial shows how to reboot your machine into another OS or grub boot menu entry directly from Ubuntu.

Say you have Ubuntu dual- or multi-boot with other operating systems, and want to reboot directly into a specific OS when working done in current Ubuntu. Or you want to reboot with another Kernel or maybe recovery mode without any keyboard press while booting. This tutorial may help.

Method 1: Single command to reboot into another OS

Grub, the default boot-loader for many Linux, has a command line tool grub-reboot, which allows to set the default boot-entry for ONLY next boot.

Along with reboot command, it allows to reboot directly into another entry. For example, reboot into the third menu try with command:

sudo grub-reboot 2 && reboot

NOTE: Grub menu entry counts from 0. Number 2 means the 3rd entry.

Tell which number for booting your OS/entry

You don’t have to reboot and count in the boot-menu for your desired number. There are 2 ways to view the menu from in Ubuntu.

Option 1. Preview Grub Menu via Grub-Emu

Press Ctrl+Alt+T on keyboard to open terminal, and run command to install grub-emu:

sudo apt install grub-emu

Then, run grub-emu command in terminal will open up a window for previewing your boot-loader. And, close the terminal will also close the preview window.

Option 2. Use Grub-Customizer

Grub-Customizer is a good alternative, as the preview tool does not work good in my case. To install it, open terminal (Ctrl+Alt+T) and run 3 commands below one by one.

The commands will add the software developer’s PPA repository, update cache and finally install it into your system.

sudo add-apt-repository ppa:danielrichter2007/grub-customizer

sudo apt update

sudo apt install grub-customizer

After that, search for and open it from either system start menu or ‘Activities’ overview depends on your DE.

As the screenshot shows you, number 2 is for Windows in my case. 1>1 means recovery mode, and 1>2 means the previous kernel entry.

So, run the command below will reboot directly into Windows in my case:

sudo grub-reboot 2 && reboot

To reboot into recovery mode in sub-menu entry (quotation marks required), use:

sudo grub-reboot "1>1" && reboot

And, if you want to use the command in script or bind with a keyboard shortcut, use command:

pkexec grub-reboot 2 && reboot

So, it will pop-up an authentication dialog asks you to type user password, before performing the action.

Method 2: Add Reboot option in top-right system menu

For GNOME 43, meaning users of Ubuntu 22.10, Fedora 37, Arch and Manjaro Linux, there’s an extension to do the job by adding menu entries into system status menu.

By clicking on an entry in the menu, will pop-up password authentication dialog, and then shows you the reboot dialog. When typing correct password and click restart in pop-up dialog, it reboot directly with that entry you just clicked!

How to Install the Extension

For Ubuntu 22.10, first search for and install “Extension Manager” from Ubuntu Software.

Then press Super (the Windows Logo) key to activate overview, search for and open “Extension Manager”. Finally, use the tool to install the “Custom Reboot” extension:

For Fedora 37 and other Linux with GNOME 43, you may go directly to the extension website and use ON/OFF switch to install it.