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DEVFS(8)		FreeBSD	System Manager's Manual		      DEVFS(8)

     devfs -- DEVFS control

     devfs [-m mount-point] keyword argument ...

     The devfs utility provides	an interface to	manipulate properties of
     devfs(5) mounts.

     The keyword argument determines the context for the rest of the argu-
     ments.  For example, most of the commands related to the rule subsystem
     must be preceded by the rule keyword.  The	following flags	are common to
     all keywords:

	   -m mount-point
		       Operate on mount-point, which is	expected to be a
		       devfs(5)	mount.	If this	option is not specified, devfs
		       operates	on /dev.

   Rule	Subsystem
     The devfs(5) rule subsystem provides a way	for the	administrator of a
     system to control the attributes of DEVFS nodes.  Each DEVFS mount-point
     has a ``ruleset'',	or a list of rules, associated with it.	 When a	device
     driver creates a new node,	all the	rules in the ruleset associated	with
     each mount-point are applied (see below) before the node becomes visible
     to	the userland.  This permits the	administrator to change	the proper-
     ties, including the visibility, of	certain	nodes.	For example, one might
     want to hide all disk nodes in a jail(2)'s	/dev.

   Rule	Manipulation
     Rule manipulation commands	follow the rule	keyword.  The following	flags
     are common	to all of the rule manipulation	commands:

	   -s ruleset  Operate on the ruleset with the number ruleset.	If
		       this is not specified, the commands operate on the
		       ruleset currently associated with the specified mount-

     The following commands are	recognized:

	   rule	add [rulenum] rulespec
		       Add the rule described by rulespec (defined below) to
		       the ruleset.  The rule has the number rulenum if	it is
		       explicitly specified; otherwise,	the rule number	is
		       automatically determined	by the kernel.

	   rule	apply rulenum |	rulespec
		       Apply rule number rulenum or the	rule described by
		       rulespec	to the mount-point.  Rules that	are
		       ``applied'' have	their conditions checked against all
		       nodes in	the mount-point	and the	actions	taken if they

	   rule	applyset
		       Apply all the rules in the ruleset to the mount-point
		       (see above for the definition of	``apply'').

	   rule	del rulenum
		       Delete rule number rulenum from the ruleset.

	   rule	delset
		       Delete all rules	from the ruleset.

	   rule	show [rulenum]
		       Display the rule	number rulenum,	or all the rules in
		       the ruleset.  The output	lines (one line	per rule) are
		       expected	to be valid rulespecs.

	   rule	showsets
		       Report the numbers of existing rulesets.

	   ruleset ruleset
		       Set ruleset number ruleset as the current ruleset for
		       the mount-point.

   Rule	Specification
     Rules have	two parts: the conditions and the actions.  The	conditions
     determine which DEVFS nodes the rule matches 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 ``operator'' for all devices of type
     tape.  If the first token of a rule specification is a single dash	(`-'),
     rules are read from the standard input and	the rest of the	specification
     is	ignored.

     The following conditions are recognized.  Conditions are ANDed together
     when matching a device; if	OR is desired, multiple	rules can be written.

	   path	pattern
		       Matches any node	with a path that matches pattern,
		       which is	interpreted as a glob(3)-style pattern.

	   type	devtype
		       Matches any node	that is	of type	devtype.  Valid	types
		       are disk, mem, tape and tty.

     The following actions are recognized.  Although there is no explicit
     delimiter between conditions and actions, they may	not be intermixed.

	   group gid   Set the GID of the node to gid, which may be a group
		       name (looked up in /etc/group) or number.

	   hide	       Hide the	node.  Nodes may later be revived manually
		       with mknod(8) or	with the unhide	action.

	   include ruleset
		       Apply all the rules in ruleset number ruleset to	the
		       node.  This does	not necessarily	result in any changes
		       to the node (e.g., if none of the rules in the included
		       ruleset match).

	   mode	filemode
		       Set the file mode to filemode, which is interpreted as
		       in chmod(1).

	   user	uid    Set the UID to uid, which may be	a user name (looked up
		       in /etc/passwd) or number.

	   unhide      Unhide the node.

     Rulesets are created by the kernel	at the first reference and destroyed
     when the last reference disappears.  E.g.,	a ruleset is created when a
     rule is added to it or when it is set as the current ruleset for a	mount-
     point, and	a ruleset is destroyed when the	last rule in it	is deleted and
     no	other references to it exist (i.e., it is not included by any rules
     and it is not the current ruleset for any mount-point).

     Ruleset number 0 is the default ruleset for all new mount-points.	It is
     always empty, cannot be modified or deleted, and does not show up in the
     output of showsets.

     Rules and rulesets	are unique to the entire system, not a particular
     mount-point.  I.e., a showsets will return	the same information regard-
     less of the mount-point specified with -m.	 The mount-point is only rele-
     vant when changing	what its current ruleset is or when using one of the
     apply commands.

     /etc/defaults/devfs.rules	       Default devfs configuration file.
     /etc/devfs.rules		       Local devfs configuration file.
     /etc/devfs.conf		       Boot-time devfs configuration file.
				       Example boot-time devfs configuration

     When the system boots, the	only ruleset that exists is ruleset number 0;
     since the latter may not be modified, we have to create another ruleset
     before adding rules.  Note	that since most	of the following examples do
     not specify -m, the operations are	performed on /dev (this	only matters
     for things	that might change the properties of nodes).

	   devfs ruleset 10

     Specify that ruleset 10 should be the current ruleset for /dev (if	it
     does not already exist, it	is created).

	   devfs rule add path speaker mode 666

     Add a rule	that causes all	nodes that have	a path that matches
     ``speaker'' (this is only /dev/speaker) to	have the file mode 666 (read
     and write for all).  Note that if any such	nodes already exist, their
     mode will not be changed unless this rule (or ruleset) is explicitly
     applied (see below).  The mode will be changed if the node	is created
     after the rule is added (e.g., the	atspeaker module is loaded after the
     above rule	is added).

	   devfs rule applyset

     Apply all the rules in the	current	ruleset	to all the existing nodes.
     E.g., if the above	rule was added after /dev/speaker was created, this
     command will cause	its file mode to be changed to 666 as prescribed by
     the rule.

	   devfs rule add path snp* mode 660 group snoopers

     (Quoting the argument to path is often necessary to disable the shell's
     globbing features.)  For all devices with a path that matches ``snp*'',
     set the file mode to 660 and the GID to ``snoopers''.  This permits users
     in	the ``snoopers'' group to use the snp(4) devices.

	   devfs rule -s 20 add	type disk group	wheel

     Add a rule	to ruleset number 20.  Since this ruleset is not the current
     ruleset for any mount-points, this	rule is	never applied automatically
     (unless ruleset 20	becomes	a current ruleset for some mount-point at a
     later time).  However, it can be applied explicitly, as such:

	   devfs -m /my/jail/dev rule -s 20 applyset

     This will apply all rules in ruleset number 20 to the DEVFS mount on
     /my/jail/dev.  It does not	matter that ruleset 20 is not the current
     ruleset for that mount-point; the rules are still applied.

	   devfs rule apply hide

     Since this	rule has no conditions,	the action (hide) will be applied to
     all nodes.	 Since hiding all nodes	is not very useful, we can undo	it:

	   devfs rule apply unhide

     which applies unhide to all the nodes, causing them to reappear.

	   devfs rule -s 10 add	- < my_rules

     Add all the rules from the	file my_rules to ruleset 10.

	   devfs rule -s 20 show | devfs rule -s 10 add	-

     Since show	outputs	valid rules, this feature can be used to copy rule-
     sets.  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).

     chmod(1), jail(2),	glob(3), devfs(5), devfs.conf(5), devfs.rules(5),
     chown(8), jail(8),	mknod(8)

     Dima Dorfman

FreeBSD	7.2			 July 1, 2008			   FreeBSD 7.2


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