1 files changed, 26 insertions, 0 deletions

diff --git a/sbin/devfs/devfs.8 b/sbin/devfs/devfs.8
index 11cede3563891..b22a9ad89e0a0 100644
--- a/sbin/devfs/devfs.8
+++ b/sbin/devfs/devfs.8
@@ -143,6 +143,10 @@ and the actions determine what should be done when a rule matches a node.
 For example, a rule can be written that sets the GID to
 .Li games
 for all devices with major number 53.
+If the first token of a rule specification is a single dash
+.Pq Dq - ,
+rules are read from the standard input and the rest of the specification
+is ignored.
 .Pp
 The following conditions are recognized.
 Conditions are ANDed together when matching a device;
@@ -311,6 +315,28 @@ will be applied to all nodes.
 Since hiding all nodes isn't very useful, we can undo like so:
 .Pp
 .Dl devfs rule apply unhide
+.Pp
+which applies
+.Cm unhide
+to all the nodes,
+causing them to reappear.
+.Pp
+.Dl cat my_rules | devfs rule -s 10 add -
+.Pp
+Add all the rules from the file
+.Pa my_rules
+to ruleset 10.
+.Pp
+.Dl devfs rule -s 20 show | devfs rule -s 10 add -
+.Pp
+Since
+.Cm show
+outputs valid rules,
+this feature can be used to copy rulesets.
+The above copies all the rules from ruleset 20 into ruleset 10.
+The rule numbers are preserved,
+but ruleset 10 may already have rules with non-conflicting numbers
+(these will be preserved).
 .Sh SEE ALSO
 .Xr jail 2 ,
 .Xr glob 3 ,