Add a block device or virtual machine image.
+The format of the disk image is auto-detected. To override this and
+force a particular format use the I<--format=..> option.
+
=item B<--dir-cache-timeout N>
Set the readdir cache timeout to I<N> seconds, the default being 60
(see the FUSE option I<-o attr_timeout>), but the FUSE cache
does not anticipate future requests, only cache existing ones.
+=item B<--format=raw|qcow2|..> | B<--format>
+
+The default for the I<-a> option is to auto-detect the format of the
+disk image. Using this forces the disk format for I<-a> options which
+follow on the command line. Using I<--format> with no argument
+switches back to auto-detection for subsequent I<-a> options.
+
+If you have untrusted raw-format guest disk images, you should use
+this option to specify the disk format. This avoids a possible
+security problem with malicious guests (CVE-2010-3851). See also
+L</add-drive-opts>.
+
=item B<--fuse-help>
Display help on special FUSE options (see I<-o> below).