Add important policies tip for udisksctl

Without knowledge of this, people trying out an Ubuntu- or Debian-based
distribution will be frustrated when trying to use udisksctl(1). I ran
into this situation myself, so discovering this was a relief.

sheets/udisksctl

@@ -1,20 +1,34 @@
+# udisksctl
+# The udisks command line tool
+
 # Output low-level information for the provided block device and partition.
 udisksctl info -b /dev/sdd1
 
-# Mount partition on the given block device. This will by default use '/media', and
-# on typical systems won't even require root privileges.
+# Mount partition on the given block device. This will by default use
+# '/media', and on typical systems won't even require root privileges.
 udisksctl mount -b /dev/sd??
 
 # Set up a loop device using 'imagefile'. This only sets it up, so you will
-# probably also want to mount it thereafter, using the device given to you after
-# executing this command. often, if not always, this is '/dev/loopX', where X is
-# the loop device number.
+# probably also want to mount it thereafter, using the device given to you
+# after executing this command. often, if not always, this is '/dev/loopX', -
+# where X is the loop device number.
 udisksctl loop-setup -f image file
 
 # Like the above, except this will delete the loop device (assuming 'loop0' was
-# previously created) but note that this will NOT delete the image file. Be sure to
-# unmount the filesystem(s) on the device first, before deleting it.
+# previously created) but note that this will NOT delete the image file. Be
+# sure to unmount the filesystem(s) on the device first, before deleting it.
 udisksctl loop-delete -b /dev/loop0
 
-# Power off a block device. May not work for all devices, and may vary in effect.
+# Power off block device. May not work for all devices, and may vary in effect.
 udisksctl power-off -b /dev/sdb
+
+# Example of a suitable mount request for auto-mounting at startup. Useful if
+# fstab isn't playing nice. This also demonstrates using `mount`-style options.
+udisksctl mount --no-user-interaction --options noatime -b /dev/sde1
+
+# In some distributions of Linux, such as an Ubuntu 18.04 base install, will
+# not have its policies set to allow regular users to mount filesystems with
+# udisksctl(1) without root access, despite that being the point of this tool.
+# This can be resolved by updating the policies to this effect. In Ubuntu 18.04
+# it's as easy as a simple package installation procedure.
+sudo apt-get install policykit-desktop-privileges