When you try to unpack a .tar.xz file you get the following error messages:
tar (child): xz: Cannot exec: No such file or directory (child) tar: Error is not recoverable: exiting now tar: Child returned status 2 tar: Error is not recoverable: exiting now
You must solve it by installing the xz-utils
# apt - get install xz-utils
Recommended reading
-man tar