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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 /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 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 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

     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).	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.

     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.	Rule‐
				       sets 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 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

BSD			       February 21, 2010			   BSD

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