The command to decompress with xz would be:
unxz ubuntu-mate-16.04.2-desktop-armhf-raspberry-pi.img.xz
See here for more information:
https://ubuntu-mate.org/raspberry-pi/
And the man page for xz is located here:
The command to decompress with xz would be:
unxz ubuntu-mate-16.04.2-desktop-armhf-raspberry-pi.img.xz
See here for more information:
https://ubuntu-mate.org/raspberry-pi/
And the man page for xz is located here: