mutemaster: mutes the master channel
mutemic: mutes the microphone
volumedown: volume down
volumeup: volume up
run acpi_listen, press Fn+F1, Fn+F2, Fn+F3, Fn+D4. Output should be similar:
button/mute MUTE 00000080 00000000 K
button/volumedown VOLDN 00000080 00000000 K
button/volumeup VOLUP 00000080 00000000 K
button/f20 F20 00000080 00000000 K
cp mutem* volume* /etc/acpi/events/
apt-get install amixer
systemctl restart acpid