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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

           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 ``games'' for all devices with major num-
     ber 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 speci-
     fication 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
     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 in

           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