Command Section
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
     arguments.  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
     properties, 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
                      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 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.  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
     regardless of the mount-point specified with -m.  The mount-point is only
     relevant 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
                                            configuration 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
     applied 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 11.1-RELEASE-p4         October 5, 2016        FreeBSD 11.1-RELEASE-p4
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