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DEVFS(8)		  BSD 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

   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 cur-
		   rently 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 explic-
		   itly	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 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 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

   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 "games" for all devices with major	number
     53.  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.

	   major majdev
		   Matches any node with a major number	equal to majdev.

	   path	pattern
		   Matches any node with a path	that matches pattern.  The
		   latter 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.

	   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 in oc-

	   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; 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.

     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 rule pre-

	   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 more 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	major 53 group games

     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 applied regardless.

	   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	like

	   devfs rule apply unhide

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

	   cat my_rules	| devfs	rule -s	10 add -

     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), chown(8), jail(8), mknod(8)

     Dima Dorfman

BSD				 July 1, 2002				   BSD


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