ecco quello che mi dice dopo aver messo apt-get install x-window-system xfs:

Reading package list... Done
Building depency tree
Reading state information... Done
Note, selecting xorg instead of x-window-system
xorg is already the newest version.
Package xfs is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or is only available from another source
E: package xfs has no installation candidate