Provided by: udev_124-8_i386 bug

NAME

       udev - dynamic device management

DESCRIPTION

       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.

CONFIGURATION

       All udev configuration files are placed in /etc/udev/*. Every file
       consists of a set of lines of text. All empty lines or lines beginning
       with ´#´ will be ignored.

   Configuration file
       udev expects its main configuration file at /etc/udev/udev.conf. It
       consists of a set of variables allowing the user to override default
       udev values. The following variables can be set:

       udev_root
           Specifies where to place the device nodes in the filesystem. The
           default value is /dev.

       udev_rules
           The name of the udev rules file or directory to look for files with
           the suffix .rules. Multiple rule files are read in lexical order.
           The default value is /etc/udev/rules.d.

       udev_log
           The logging priority. Valid values are the numerical syslog
           priorities or their textual representations: err, info and debug.

   Rules files
       The udev rules are read from the files located in the /etc/udev/rules.d
       directory or at the location specified value in the configuration file.
       Every line in the rules file contains at least one key value pair.
       There are two kind of keys, match and assignment keys. 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 rule may consist 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 operators are:

       ==
           Compare for equality.

       !=
           Compare for non-equality.

       =
           Assign a value to a key. Keys that represent a list, are reset and
           only this single value is assigned.

       +=
           Add the value to a key that holds a list of entries.

       :=
           Assign a value to a key finally; disallow any later changes, which
           may be used to prevent changes by any later rules.

       The following key names can be used to match against device properties.
       Some of the keys also match against properties of the parent devices in
       sysfs, not only the device that has generated the event. If multiple
       keys that match a parent device are specified in a single rule, all
       these keys must match at one and the same parent device.

       ACTION
           Match the name of the event action.

       DEVPATH
           Match the devpath of the event device.

       KERNEL
           Match the name of the event device.

       NAME
           Match the name of the node or network interface. It can be used
           once the NAME key has been set in one of the preceding rules.

       SUBSYSTEM
           Match the subsystem of the event device.

       DRIVER
           Match the driver name of the event device. Only set for devices
           which are bound to a driver at the time the event is generated.

       ATTR{filename}
           Match sysfs attribute values of the event device. Up to five ATTR
           keys can be specified per rule. Trailing whitespace in the
           attribute values is ignored, if the specified match value does not
           contain trailing whitespace itself. Depending on the type of
           operator, this key is also used to set the value of a sysfs
           attribute.

       KERNELS
           Search the devpath upwards for a matching device name.

       SUBSYSTEMS
           Search the devpath upwards for a matching device subsystem name.

       DRIVERS
           Search the devpath upwards for a matching device driver name.

       ATTRS{filename}
           Search the devpath upwards for a device with matching sysfs
           attribute values. Up to five ATTRS keys can be specified per rule,
           but all of them must match on the same device. Trailing whitespace
           in the attribute values is ignored, if the specified match value
           does not contain trailing whitespace itself.

       ENV{key}
           Match against the value of an environment variable. Up to five ENV
           keys can be specified per rule. Depending on the type of operator,
           this key is also used to export a variable to the environment.

       TEST{octal mode mask}
           Test the existence of a file. An octal mode mask can be specified
           if needed.

       PROGRAM
           Execute external program. The key is true, if the program returns
           with exit code zero. The whole event environment is available to
           the executed program. The program´s output printed to stdout, is
           available in the RESULT key.

       RESULT
           Match the returned string of the last PROGRAM call. This key can be
           used in the same or in any later rule after a PROGRAM call.

       Most of the fields support a shell style pattern matching. The
       following pattern characters are supported:

       *
           Matches zero, or any number of characters.

       ?
           Matches any single character.

       []
           Matches any single character specified within the brackets. For
           example, the pattern string ´tty[SR]´ would match either ´ttyS´ or
           ´ttyR´. Ranges are also supported within this match with the ´-´
           character. For example, to match on the range of all digits, the
           pattern [0-9] would be used. If the first character following the
           ´[´ is a ´!´, any characters not enclosed are matched.

       The following keys can get values assigned:

       NAME
           The name of the node to be created, or the name the network
           interface should be renamed to. Only one rule can set the node
           name, all later rules with a NAME key will be ignored.

       SYMLINK
           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.

       OWNER, GROUP, MODE
           The permissions for the device node. Every specified value
           overwrites the compiled-in default value.

       ATTR{key}
           The value that should be written to a sysfs attribute of the event
           device. Depending on the type of operator, this key is also used to
           match against the value of a sysfs attribute.

       ENV{key}
           Export a variable to the environment. Depending on the type of
           operator, this key is also to match against an environment
           variable.

       RUN
           Add a program to the list of programs to be executed for a specific
           device. This can only be used for very short running tasks. Running
           an event process for a long period of time may block all further
           events for this or a dependent device. Long running tasks need to
           be immediately detached from the event process itself.

           If the specifiefd string starts with socket:path, 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.

       LABEL
           Named label where a GOTO can jump to.

       GOTO
           Jumps to the next LABEL with a matching name

       IMPORT{type}
           Import a set of variables into the event environment, depending on
           type:

           program
               Execute an external program specified as the assigned value and
               import its output, which must be in environment key format.

           file
               Import a text file specified as the assigned value, which must
               be in environment key format.

           parent
               Import the stored keys from the parent device by reading the
               database entry of the parent device. The value assigned to
               IMPORT{parent} is used as a filter of key names to import (with
               the same shell-style pattern matching used for comparisons).

           If no option is given, udev will choose between program and file
           based on the executable bit of the file permissions.

       WAIT_FOR
           Wait for a file to become available.

       OPTIONS
           Rule and device options:

           last_rule
               Stops further rules application. No later rules will have any
               effect.

           ignore_device
               Ignore this event completely.

           ignore_remove
               Do not remove the device node when the device goes away. This
               may be useful as a workaround for broken device drivers.

           link_priority=value
               Specify the priority of the created symlinks. Devices with
               higher priorities overwrite existing symlinks of other devices.

           all_partitions
               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.

           event_timeout=
               Number of seconds an event will wait for operations to finish,
               before it will terminate itself.

           string_escape=none|replace
               Usually control and other possibly unsafe characters are
               replaced in strings used for device naming. The mode of
               replacement can be specified with this option.

       The NAME, SYMLINK, PROGRAM, OWNER, GROUP, MODE and RUN fields support
       simple printf-like string substitutions. The RUN format chars gets
       applied after all rules have been processed, right before the program
       is executed. It allows the use of the complete environment set by
       earlier matching rules. For all other fields, substitutions are applied
       while the individual rule is being processed. The available
       substitutions are:

       $kernel, %k
           The kernel name for this device.

       $number, %n
           The kernel number for this device. For example, ´sda3´ has kernel
           number of ´3´

       $devpath, %p
           The devpath of the device.

       $id, %b
           The name of the device matched while searching the devpath upwards
           for SUBSYSTEMS, KERNELS, DRIVERS and ATTRS.

       $driver
           The driver name of the device matched while searching the devpath
           upwards for SUBSYSTEMS, KERNELS, DRIVERS and ATTRS.

       $attr{file}, %s{file}
           The value of a sysfs attribute found at the device, where all keys
           of the rule have matched. If the matching device does not have such
           an attribute, all devices along the chain of parents are searched
           for a matching attribute. If the attribute is a symlink, the last
           element of the symlink target is returned as the value.

       $env{key}, %E{key}
           The value of an environment variable.

       $major, %M
           The kernel major number for the device.

       $minor, %m
           The kernel minor number for the device.

       $result, %c
           The string returned by the external program requested with PROGRAM.
           A single part of the string, separated by a space character may be
           selected by specifying the part number as an attribute: %c{N}. If
           the number is followed by the ´+´ char this part plus all remaining
           parts of the result string are substituted: %c{N+}

       $parent, %P
           The node name of the parent device.

       $name
           The current name of the device node. If not changed by a rule, it
           is the name of the kernel device.

       $links
           The current list of symlinks, separated by a space character. The
           value is only set if an earlier rule assigned a value, or during a
           remove events.

       $root, %r
           The udev_root value.

       $sys, %S
           The sysfs mount point.

       $tempnode, %N
           The name of a created temporary device node to provide access to
           the device from a external program before the real node is created.

       %%
           The ´%´ character itself.

       $$
           The ´$´ character itself.

       The count of characters to be substituted may be limited by specifying
       the format length value. For example, ´%3s{file}´ will only insert the
       first three characters of the sysfs attribute

AUTHOR

       Written by Greg Kroah-Hartman <greg@kroah.com> and Kay Sievers
       <kay.sievers@vrfy.org>. With much help from Dan Stekloff and many
       others.

SEE ALSO

       udevd(8), udevadm(8)