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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-point.

     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 au-
		      tomatically 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	match.

     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 ex-
		      pected 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 de-
     termine 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 ig-

     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 de-
     limiter 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.  Hiding a directory
		      node effectively hides all of its	child nodes.

     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).  Include commands	in the referenced
		      ruleset are not resolved.

     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.	If the node resides in a subdirectory,
		      all parent directory nodes must be visible to be able to
		      access 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.
					    Rulesets in	here override those in
					    /etc/defaults/devfs.rules with the
					    same ruleset number, otherwise the
					    two	files are effectively merged.
     /etc/devfs.conf			    Boot-time devfs configuration
     /usr/share/examples/etc/devfs.conf	    Example boot-time devfs configura-
					    tion file.

     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).

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

	   devfs ruleset 10

     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 add path speaker mode 666

     Apply all the rules in the	current	ruleset	to all the existing nodes.
     E.g., if the below	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 applyset

     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 (quoting the argument to path is often necessary
     to	disable	the shell's globbing features):

	   devfs rule add path snp* mode 660 group snoopers

     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):

	   devfs rule -s 20 add	type disk group	wheel

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

     Since the following rule has no conditions, the action (hide) will	be ap-
     plied to all nodes:

	   devfs rule apply hide

     Since hiding all nodes is not very	useful,	we can undo it.	 The following
     applies unhide to all the nodes, causing them to reappear:

	   devfs rule apply unhide

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

	   devfs rule -s 10 add	- < my_rules

     The below 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).  Since show	outputs	valid
     rules, this feature can be	used to	copy rulesets:

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

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

     The devfs utility first appeared in FreeBSD 5.0.

     Dima Dorfman

FreeBSD	13.0			October	5, 2016			  FreeBSD 13.0


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