To set the ACPI OS string to Windows 2015 on Linux, you must modify the kernel command line in your bootloader configuration. This involves adding the parameter
acpi_osi="Windows 2015" to the GRUB configuration file and then updating the GRUB boot loader. After applying these changes, rebooting the system ensures the new operating system identification string is passed to the firmware during startup, allowing hardware compatibility layers to recognize the system as a Windows environment.
Understanding the ACPI OSI Mechanism
The Advanced Configuration and Power Interface (ACPI) includes a feature called OSI (Operating System Identification). When a Linux kernel boots, it queries the BIOS/UEFI firmware for specific capabilities. The firmware expects an identifier for the operating system it is running. By default, most Linux distributions send their own distribution name or a generic Linux identifier. However, some hardware vendors implement workarounds in their firmware that only activate certain features, such as keyboard backlight controls, touchpad gestures, or Wi-Fi power management, if they detect a specific version of Microsoft Windows.
Setting the ACPI OS string to
Windows 2015 tricks the firmware into believing it is running on Windows 10 (which corresponds to the 2015 OSI string revision). This is a common troubleshooting step for laptops where hardware functions fail under Linux but work perfectly under Windows. It is important to note that this change does not install Windows; it merely alters the handshake protocol between the kernel and the motherboard firmware.
Locating and Editing the GRUB Configuration
The primary method for injecting this parameter is through the GRand Unified Bootloader (GRUB), which is the standard bootloader for most Debian-based and Red Hat-based Linux distributions. You need to edit the main configuration file that defines how the kernel is loaded.
Open a terminal and use a text editor with root privileges to edit the GRUB defaults file. For most systems, this file is located at
/etc/default/grub. You can use
nano or
vim depending on your preference:
sudo nano /etc/default/grub
Once the file is open, locate the line that begins with
GRUB_CMDLINE_LINUX_DEFAULT. This line contains the arguments passed to the kernel when booting the default entry. It typically looks something like this:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
You need to append the ACPI OSI string to this list. Ensure there is a space before the new parameter. Modify the line to include the following value:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=\"Windows 2015\""
If you have other parameters already listed, simply add the new one separated by a space. Be careful with the quotation marks. The outer quotes define the entire string argument, while the inner escaped quotes
\" ensure that the firmware receives the literal string "Windows 2015" without the shell interpreting them incorrectly. Save the file and exit the editor.
Updating GRUB and Applying Changes
Editing the configuration file alone does not apply the changes immediately. GRUB generates its actual boot configuration from this source file every time you update it. You must run the update command specific to your distribution.
For Debian, Ubuntu, Linux Mint, and other derivatives, run:
sudo update-grub
For Fedora, RHEL, CentOS, and openSUSE systems, the command is slightly different:
sudo grub2-mkconfig -o /boot/grub2/grub.cfg
On older systems or those using legacy BIOS rather than UEFI, you might need to use
sudo grub-mkconfig -o /boot/grub/grub.cfg. If you are unsure which command works, check your distribution's documentation, but
update-grub is the most common for general users.
After the command completes successfully, you should see output indicating that the configuration has been updated. No immediate reboot is required to finish the process, but the changes will not take effect until the next boot cycle.
Verifying the Change
Reboot your computer. Once the system is back up, you can verify that the kernel received the correct parameter. Use the
dmesg command to search the kernel ring buffer for ACPI-related messages.
dmesg | grep -i acpi_osi
You should see a line indicating that the OS name was set to Windows 2015. Additionally, you can check the current OS string exposed to the firmware by reading the virtual file:
cat /sys/firmware/acpi/tables/_OSI
This file should contain the string "Windows 2015". If you previously tried setting this via other methods and found that
dmesg | grep -i added did not show results, it is likely because the parameter was not being passed correctly at boot time or was overridden by a later kernel module. Using the GRUB method ensures the parameter is present from the earliest stages of kernel initialization.
Note that if you use Secure Boot, ensure that your kernel and GRUB signatures are valid, as unsigned modifications to boot configurations may be rejected by the firmware. Most standard repositories provide signed kernels that handle this automatically.
Frequently Asked Questions
What happens if I set the wrong OSI string?
If you set an incorrect or non-existent OSI string, the firmware will likely treat the system as a generic Linux machine. This usually means no harm is done, but you may lose access to hardware-specific features that rely on Windows detection. Always use documented strings like "Windows 2015" or "Windows 2018" to avoid unexpected behavior.
Can I change the OSI string dynamically without rebooting?
No, the ACPI OSI string is determined during the early boot phase when the kernel initializes the firmware interface. Changing it requires a full reboot to reload the kernel with the new command-line arguments. There is no runtime switch to alter this value once the system is running.
Why doesn't my laptop keyboard backlight work after changing the string?
Changing the OSI string is just one part of the solution. Some hardware requires additional kernel modules or specific driver versions to function correctly. If the backlight still does not respond, check if the
acpi_backlight=vendor parameter is also needed in your GRUB configuration alongside the OSI string.
Will this affect dual-boot setups with Windows?
No, this change only affects the Linux kernel's interaction with the firmware. When you boot into Windows, the Windows kernel handles its own ACPI initialization independently. Your Windows installation remains unaffected by the Linux GRUB settings.
How do I revert this change if it causes issues?
To revert the change, edit
/etc/default/grub again and remove the
acpi_osi="Windows 2015" portion from the
GRUB_CMDLINE_LINUX_DEFAULT line. Then, run
sudo update-grub (or your distribution's equivalent) and reboot. The system will return to sending the default Linux OSI identifier.