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diff --git a/udev/udev.xml b/udev/udev.xml
index 0ea5892c7..678023c37 100644
--- a/udev/udev.xml
+++ b/udev/udev.xml
@@ -18,23 +18,28 @@
udev
- dynamic device management
+ Linux dynamic device managementDESCRIPTION
- udev provides a dynamic device directory containing only the files for
- actually present devices. It creates or removes device node files in the
- /dev directory, or it renames network interfaces.
-
- Usually udev runs as udevd
- 8 and receives uevents directly from the
- kernel if a device is added or removed from the system.
-
- If udev receives a device event, it matches its configured rules
- against the available device attributes provided in sysfs to identify the device.
- Rules that match may provide additional device information or specify a device
- node name and multiple symlink names and instruct udev to run additional programs
- as part of the device event handling.
+ udev supplies the system software with device events, manages permissions
+ of device nodes and may create additional symlinks in the /dev
+ directory, or renames network interfaces. The kernel usually just assigns unpredictable
+ device names based on the order of discovery. Meaningful symlinks or network device
+ names provide a way to reliably identify devices based on their properties or
+ current configuration.
+
+ The udev daemon udevd
+ 8 receives device uevents directly from
+ the kernel whenever a device is added or removed from the system, or it changes its
+ state. When udev receives a device event, it matches its configured set of rules
+ against various device attributes to identify the device. Rules that match, may
+ provide additional device information to be stored in the udev database, or information
+ to be used to create meaningful symlink names.
+
+ All device information udev processes, is stored in the udev database and
+ sent out to possible event subscribers. Access to all stored data and the event
+ sources are provided by the library libudev.CONFIGURATION
@@ -84,9 +89,9 @@
If all match keys are matching against its value, the rule gets applied and the
assign keys get the specified value assigned.
- A matching rule may specify the name of the device node, add a symlink
- pointing to the node, or run a specified program as part of the event handling.
- If no matching rule is found, the default device node name is used.
+ A matching rule may rename a network interface, add symlinks
+ pointing to the device node, or run a specified program as part of
+ the event handling.A rule consists of a list of one or more key value pairs separated by
a comma. Each key has a distinct operation, depending on the used operator. Valid
@@ -166,6 +171,16 @@
+
+
+
+ Match the name of a symlink targeting the node. It can
+ be used once a SYMLINK key has been set in one of the preceding
+ rules. There may be multiple symlinks; only one needs to match.
+
+
+
+
@@ -227,6 +242,13 @@
+
+
+
+ Match against a device tag.
+
+
+
@@ -287,18 +309,34 @@
- The name of the node to be created, or the name the network interface
- should be renamed to.
+ The name, a network interface should be renamed to. Or as
+ a temporary workaraound, the name a device node should be named.
+ Usually the kernel provides the defined node name, or even creates
+ and removes the node before udev even receives any event. Changing
+ the node name from the kernel's default creates inconsistencies
+ and is not supported. If the kernel and NAME specify different names,
+ an error will be logged. Udev is only expected to handle device node
+ permissions and to create additional symlinks, not to change
+ kernel-provided device node names. Instead of renaming a device node,
+ SYMLINK should be used. Symlink names must never conflict with
+ device node names, it will result in unpredictable behavior.
- The name of a symlink targeting the node. Every matching rule can add
- this value to the list of symlinks to be created along with the device node.
- Multiple symlinks may be specified by separating the names by the space
- character.
+ The name of a symlink targeting the node. Every matching rule will add
+ this value to the list of symlinks to be created. Multiple symlinks may be
+ specified by separating the names by the space character. In case multiple
+ devices claim the same name, the link will always point to the device with
+ the highest link_priority. If the current device goes away, the links will
+ be re-evaluated and the device with the next highest link_priority will own
+ the link. If no link_priority is specified, the order of the devices, and
+ which one of them will own the link, is undefined. Claiming the same name for
+ a symlink, which is or might be used for a device node, may result in
+ unexpected behavior and is not supported.
+
@@ -326,6 +364,19 @@
+
+
+
+ Attach a tag to a device. This is used to filter events for users
+ of libudev's monitor functionality, or to enumerate a group of tagged
+ devices. The implementation can only work efficiently if only a few
+ tags are attached to a device. It is only meant to be used in
+ contexts with specific device filter requirements, and not as a
+ general-purpose flag. Excessive use might result in inefficient event
+ handling.
+
+
+
@@ -337,12 +388,10 @@
is
specified, and the executed program returns non-zero, the event will be
marked as failed for a possible later handling.
- If the specified string starts with
- , all current event
- values will be passed to the specified socket, as a message in the same
- format the kernel sends an uevent. If the first character of the specified path
- is an @ character, an abstract namespace socket is used, instead of an existing
- socket file.
+ If no absolute path is given, the program is expected to live in
+ /lib/udev, otherwise the absolute path must be
+ specified. Program name and arguments are separated by spaces. Single quotes
+ can be used to specify arguments with spaces.
@@ -370,7 +419,9 @@
Execute an external program specified as the assigned value and
- import its output, which must be in environment key format.
+ import its output, which must be in environment key
+ format. Path specification, command/argument separation,
+ and quoting work like in .
@@ -380,6 +431,14 @@
environment key format.
+
+
+
+ Import a single property specified as the assigned value from the
+ current device database. This works only if the database is already populated
+ by an earlier event.
+
+
@@ -400,7 +459,8 @@
- Wait for a file to become available.
+ Wait for a file to become available or until a 10
+ seconds timeout expires.
@@ -409,26 +469,6 @@
Rule and device options:
-
-
-
- Stops further rules application. No later rules will have
- any effect.
-
-
-
-
-
- Ignore this event completely.
-
-
-
-
-
- Do not remove the device node when the device goes away. This may be
- useful as a workaround for broken device drivers.
-
-
@@ -436,14 +476,6 @@
priorities overwrite existing symlinks of other devices. The default is 0.
-
-
-
- Create the device nodes for all available partitions of a block device.
- This may be useful for removable media devices where media changes are not
- detected.
-
-
@@ -463,7 +495,7 @@
Watch the device node with inotify, when closed after being opened for
- writing, a change uevent will be synthesised.
+ writing, a change uevent will be synthesised.