- Note: This article refers to the plaback mute button next to the volume control buttons. For the Microphone Mute Button present in some Thinkpad models, see Microphone Mute Button.
Starting from Linux version 2.6.23, the kernel passes the OSI string "!Linux" to ACPI (instead of "Linux"). There is a number of reasons for that (see details in drivers/acpi/osl.c in the kernel source). But IBM/Lenovo has a consistently good record of supporting Linux, so this trick is not necessary for Thinkpads. Moreover, OSI string "Linux" is needed to make the Mute button work.
For Thinkpads R61, T61 and X61, there are already hooks in drivers/acpi/blacklist.c, so no special action is required. For most other models, you need to pass the string acpi_osi="Linux" to the kernel as a boot parameter.
grub2 in Ubuntu and derivative distros
In any Ubuntu and most Ubuntu-derived distributions that use grub2, edit /etc/default/grub and add a the parameter acpi_osi="Linux" to one of these lines:
- GRUB_CMDLINE_LINUX_DEFAULT (for non-recovery boots)
- GRUB_CMDLINE_LINUX (for all boots)
Then run sudo update-grub and reboot.