=item TMPDIR
-Location of temporary directory, defaults to C</tmp>.
+Location of temporary directory, defaults to C</tmp> except for the
+cached supermin appliance which defaults to C</var/tmp>.
If libguestfs was compiled to use the supermin appliance then the
real appliance is cached in this directory, shared between all
handles belonging to the same EUID. You can use C<$TMPDIR> to
-configure another directory to use in case C</tmp> is not large
+configure another directory to use in case C</var/tmp> is not large
enough.
=back