utility provides an interface to
manipulate properties of
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
keyword. The following flags are common to all keywords:
- Operate on mount-point, which is expected
to be a
mount. If this option is not specified,
devfs operates on
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
Rule manipulation commands follow the
keyword. The following flags are common to all of the rule manipulation
- Operate on the ruleset with the number
ruleset. If this is not specified, the
commands operate on the ruleset currently associated with the specified
The following commands are recognized:
- 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.
apply rulenum |
- 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
- Apply all the rules in the ruleset to the mount-point (see above for the
definition of “apply”).
- Delete rule number rulenum from the
- Delete all rules from the ruleset.
- 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.
- Report the numbers of existing rulesets.
- Set ruleset number ruleset as the current
ruleset for the mount-point.
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 “
” 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.
- Matches any node with a path that matches
pattern, which is interpreted as a
- Matches any node that is of type devtype.
Valid types are
The following actions are recognized. Although there is no explicit delimiter
between conditions and actions, they may not be intermixed.
- Set the GID of the node to gid, which may
be a group name (looked up in
/etc/group) or number.
- Hide the node. Nodes may later be revived manually with
or with the
unhide action. Hiding a
directory node effectively hides all of its child nodes.
- 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.
- Set the file mode to filemode, which is
interpreted as in
- Set the UID to uid, which may be a user
name (looked up in /etc/passwd) or
- 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
Rules and rulesets are unique to the entire system, not a particular
mount-point. I.e., a
the same information regardless of the mount-point specified with
. The mount-point is only relevant when
changing what its current ruleset is or when using one of the apply commands.
devfs configuration file.
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.
- Example boot-time
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
, the operations are performed on
(this only matters for things that
might change the properties of nodes).
Specify that ruleset 10 should be the current ruleset for
(if it does not already exist, it is
devfs ruleset 10
Add a rule that causes all nodes that have a path that matches
” (this is only
) 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
module is loaded after the above
rule is added):
devfs rule add path speaker mode
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
”, set the file mode to 660 and the
GID to “
”. This permits users in
” group to use the
devices (quoting the argument to
often necessary to disable the shell's globbing features):
devfs rule add path snp* mode 660
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
Explicitly apply all rules in ruleset number 20 to the DEVFS mount on
. It does not matter that
ruleset 20 is not the current ruleset for that mount-point; the rules are
devfs -m /my/jail/dev rule -s 20
Since the following rule has no conditions, the action
) 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
to all the nodes, causing them to
devfs rule apply unhide
Add all the rules from the file my_rules
devfs rule -s 10 add - <
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
outputs valid rules, this feature can
be used to copy rulesets:
devfs rule -s 20 show | devfs rule -s
10 add -
utility first appeared in