# Pastebin 8i62fxih
X-*    All  options prefixed with "X-" are interpreted as comments or
              as userspace application-specific options.  These options  are
              not stored in the user space (e.g. mtab file), nor sent to the
              mount.type helpers nor  to  the  mount(2)  system  call.   The
              suggested format is X-appname.option.

       x-*    The  same  as  X-* options, but stored permanently in the user
              space. It means the options are also available for  umount  or
              another  operations.  Note that maintain mount options in user
              space is tricky, because it's  necessary  use  libmount  based
              tools  and  there  is  no  guarantee  that the options will be
              always available (for example after a move mount operation  or
              in unshared namespace).

              Note  that  before  util-linux  v2.30 the x-* options have not
              been  maintained  by  libmount  and  stored  in   user   space
              (functionality  was  the  same  as  have  X-* now), but due to
              growing number of use-cases  (in  initrd,  systemd  etc.)  the
              functionality  have  been  extended  to  keep  existing  fstab
              configurations usable without a change.