.SH NAME
udev \- Linux configurable dynamic device naming support
.SH SYNOPSIS
-.BI udev " hotplug-subsystem"
-.P
-The environment must provide the following variables:
-.TP
-.B ACTION
-.IR add " or " remove
-signifies the connection or disconnection of a device.
-.TP
-.B DEVPATH
-The sysfs devpath of the device without the mountpoint but a leading slash.
-.P
-Additional optional environment variables:
-.TP
-.B UDEV_CONFIG_FILE
-Overrides the default location of the
-.B udev
-config file.
-.TP
-.B UDEV_NO_DEVD
-The default behavior of
-.B udev
-is to execute programs in the
-.I /etc/dev.d/
-directory after device handling. If set,
-.B udev
-will skip this step.
+.BI udev
.SH "DESCRIPTION"
.B udev
provides a dynamic device directory containing only the files for actually
present devices. It creates or removes device node files usually located in
the /dev directory, or it renames network interfaces.
.br
-
.P
As part of the
.B hotplug
subsystem,
.B udev
is executed if a kernel device is added or removed from the system.
-On device creation,
+A list of rules is used to match against specific device attributes.
+.br
+On device addition,
.B udev
-reads the sysfs directory of the given device to collect device attributes
-like label, serial number or bus device number.
-These attributes may be used as keys to determine a
-unique name for the device.
+matches its configured rules against the available device attributes to
+uniquely name the device.
.B udev
-maintains a database for devices present on the system.
+maintains its own database for devices present on the system. This database
+can be queried for the relationship of the kernel device path and the
+name of the device file.
.br
On device removal,
.B udev
queries its database for the name of the device file to be deleted.
+.br
+After the device node handling, a list of collected programs specific to this
+device is executed.
.SH "CONFIGURATION"
All
.B udev
-configuration files consist of a set of lines of text. All empty
-lines and lines beginning with a '#' will be ignored.
+configuration files consist of a set of lines of text. All empty
+lines or lines beginning with '#' will be ignored.
.P
-
.B udev
expects its main configuration file at
.IR /etc/udev/udev.conf .
All rule files are read in lexical order. The default value is
.IR /etc/udev/rules.d/ .
.TP
-.B udev_permissions
-The name of the udev permission file or directory to look for files with the
-suffix
-.IR .permissions .
-All permission files are read in lexical order. The default value is
-.IR /etc/udev/permissions.d/ .
-.TP
.B udev_log
-The switch, if udev logs some information for every device handled.
+The logging priority which can be set to
+.IR "err " , "info "
+or the corresponding numerical
+.BR syslog (3)
+value.
The default value is
-.IR yes .
-.TP
-.B default_mode
-The default mode for all nodes not explicitely matching in the permissions
-file. The default value is
-.IR 0666 .
-.TP
-.B default_owner
-The default owner for all nodes not explicitely matching in the permissions
-file. The default value is
-.IR root .
-.TP
-.B default_group
-The default group for all nodes not explicitely matching in the permissions
-file. The default value is
-.IR root .
-.br
+.IR err .
.P
-.RI "A sample " udev.conf " might look like this:
+.RI "A sample " udev.conf " file might look like this:
.sp
.nf
-# udev_root - where to place the device nodes in the filesystem
-udev_root="/udev"
-
-# udev_db - The name and location of the udev database
-udev_db="/udev/.udevdb"
+# Where in the filesystem to place the device nodes
+udev_root="@udevdir@"
-# udev_rules - The name of the udev rules file or directory to look
- for files with the suffix .rules
-udev_rules="/etc/udev/rules.d/"
+# The name and location of the udev database.
+udev_db="@udevdir@/.udevdb"
-# udev_permissions - The name of the udev permission file or directory
- to look for files with the suffix .permissions
-udev_permissions="/etc/udev/udev.permissions"
+# The name and location of the udev rules file(s).
+udev_rules="@configdir@/rules.d"
-# udev_log - set to "yes" if you want logging, else "no"
-udev_log="yes"
-
-# default_mode - set the default mode for all nodes not
-# explicitely matching in the permissions file
-default_mode="0666"
-
-# default_owner - set the default owner for all nodes not
-# explicitely matching in the permissions file
-default_owner="root"
-
-# default_group - set the default group for all nodes not
-# explicitely matching in the permissions file
-default_group="root"
+# The syslog(3) priority: "err", "info", or the numerical value.
+udev_log="err"
.fi
.P
-The rules for device naming, are read from the files located in the
+The rules for device naming are read from the files located in the
.I /etc/udev/rules.d/
directory, or at the location specified by the
.I udev_rules
.br
If no matching rule is found, the default kernel device name is used.
.P
-Every rule consists of a list of comma separated fields:
+Every rule consists of a list of comma separated key value fields:
.sp
-.IR "key " ,[ "key " ,...] " name " [, " symlink" ]
+.IR "key " ,[ "key " ,...]
+.P
+Each key has the following format:
.sp
-where fields are:
+.IR "name op value"
+.P
+There are distinct key operation types, depending on the type of the key, it
+does a comparison or an assignment.
+.P
+Comparison operators are:
+.TP
+.B ==
+Compare for equality.
+.TP
+.B !=
+Compare for non-equality.
+.P
+Assignment operators are:
+.TP
+.B +=
+Add the value to a key that holds a list of entries.
+.TP
+.B :=
+Assign a value to a key finally; disallow any later changes, which
+is useful to prevent changes by any later rules.
+.TP
+.B =
+Asign a value to a key. Keys that represent a list, are reset and only this
+single value is assigned. While this operator still works inplicitely as
+comparison on keys that can't get a value assigned, its usage as an comparison
+operator is deprecated.
+.P
+The following key names can be used to match against device properties:
.TP
.B BUS
Match the bus type of the device.
.B SUBSYSTEM
Match the kernel subsystem name.
.TP
+.B ACTION
+Match the kernel action name.
+.TP
.B DRIVER
Match the kernel driver name.
.TP
.B ID
Match the device number on the bus, like PCI bus id.
.TP
-.B PLACE
-Match the topological position on bus, like physical port of USB device
-.TP
.BI SYSFS{ filename }
-Match sysfs device attribute like label, vendor, USB serial number, SCSI UUID
-or file system label. Up to 5 different sysfs files can be checked, with
-all of the values being required to match the rule.
+Match sysfs device attribute like vendor and product id's, USB serial number
+or the SCSI disk model number. Up to 5 different sysfs files can be checked,
+with all of the values being required to match the rule.
.br
Trailing whitespace characters in the sysfs attribute value are ignored, if
the key doesn't have any trailing whitespace characters by itself.
.TP
+.BI ENV{ variable }
+Match an environment variable. Up to 5 different environment variables can be
+checked, with all of the values being required to match the rule.
+.TP
.B PROGRAM
Call external program. This key is valid if the program returns successful.
The environment variables of
.B udev
-are also available for the program.
+are also available to the program.
.br
The string returned by the program may be additionally matched with the
.B RESULT
-key.
+key in the same or any later rule.
.TP
.B RESULT
Match the returned string of the last
.B PROGRAM
-call. This key may be used in any following rule after a
+call. This key can be used in the same or in any later rule after a
.B PROGRAM
call.
+.P
+The following keys can get values assigned:
.TP
.B NAME
The name of the node to be created, or the name, the network interface
-should be renamed to.
-.br
-If given with the attribute
-.BR NAME{ all_partitions }
-it will create all 15 partitions of a blockdevice.
-This may be useful for removable media devices.
+should be renamed to. Only one rule can set the a name, all later rules
+with a NAME key will be ignored.
.TP
.B SYMLINK
-The name of a symlink targeting the node. Multiple symlinks may be
-specified by separating the names by the space character.
-.br
-If both the name and the symlink fields are omitted or its
-values empty, the device will be ignored and no node will be created.
-.br
-If only the symlink field is given and the name field is omitted,
-the rule will not be applied immediatly, but the symlink field is added
-to the symlink list of the rule which will create the node.
-This makes it possible to specify additional symlinks in a possibly
-separate rules file, while the device nodes are maintained by the
-distribution provided rules file.
+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.
.TP
.B OWNER, GROUP, MODE
-The permissions for this device. Every specified value overwrites the value
-given in the permissions file.
+The permissions for the device node. Every specified value overwrites the
+compiled-in default value.
+.TP
+.B RUN
+Add a program to the list of programs to be executed for a specific device.
+.TP
+.B OPTIONS
+.B last_rule
+stops further rules application. No later rules will have any effect.
+.sp
+.B ignore_device
+will ignore this device. No node will be created or program executed.
+.sp
+.B ignore_remove
+will ignore any later remove event for this device.
+This may be useful as a workaround for broken device drivers.
+.sp
+.B all_partitions
+will create device nodes for all available partitions of a blockdevice.
+This may be useful for removable media devices which do not detect a media
+change.
+.sp
+Multiple attributes may be separated by comma.
.P
-.RB "The " NAME " ," SYMLINK " and " PROGRAM
-fields support simple printf-like string substitution:
+.RB "The " NAME ", " SYMLINK ", " PROGRAM ", " OWNER " and " GROUP
+fields support simple printf-like string substitutions:
.TP
.B %n
The "kernel number" of the device.
.B %k
The "kernel name" for the device.
.TP
+.B %p
+The devpath for the device.
+.TP
.B %M
The kernel major number for the device.
.TP
The bus id for the device.
.TP
.B %c
-The string returned from the execution of
+The string returned by the external program, specified in
.B PROGRAM
(This does not work within the
.B PROGRAM
all remaining parts of the result string are substituted:
.BI %c{ N+ }
.TP
+.B %N
+The name of a created temporary device node to provide access to the
+device from a external program.
+.TP
+.B %P
+The node name of the parent device.
+.TP
.BI %s{ filename }
The content of a sysfs attribute.
.TP
+.B %r
+The udev_root value.
+.TP
.B %e
If a device node already exists with the name, the smallest positive
decimal integer N is substituted such that the resulting name doesn't
match an existing device node. Otherwise nothing is substituted. This
can be used to create compatibility symlinks and enumerate devices of
the same type originating from different kernel subsystems.
+.sp
+Note: The use of the enumeration facility is unreliable outside of
+udevstart where the node creation is serialized and predictable.
+The returned numbers rely on the order devices are probed on the
+system. If more than one device requests an enumeration for the same
+name at the same time, it may be possible that both requests receive the
+same name back from the database. The use of enumerations in todays setups
+where device can come and go at any time is not recomended.
.TP
.B %%
The '%' character itself.
.P
-The count of charcters to insert may be limited by specifying
+The count of characters to insert may be limited by specifying
the format length value. For example, '%3s{file}' will only insert
the first three characters of the sysfs attribute.
.P
-.RI "A sample " udev.rules " might look like this:"
+.RI "A sample " udev.rules " file might look like this:"
.sp
.nf
-# if /sbin/scsi_id returns "OEM 0815" device will be called disk1
-BUS="scsi", PROGRAM="/sbin/scsi_id", RESULT="OEM 0815", NAME="disk1"
+# if /sbin/scsi_id returns "OEM 0815", the device will be called disk1
+BUS=="scsi", PROGRAM=="/sbin/scsi_id", RESULT=="OEM 0815", NAME="disk1"
# USB printer to be called lp_color
-BUS="usb", SYSFS{serial}="W09090207101241330", NAME="lp_color"
+BUS=="usb", SYSFS{serial}=="W09090207101241330", NAME="lp_color"
# SCSI disk with a specific vendor and model number will be called boot
-BUS="scsi", SYSFS{vendor}="IBM", SYSFS{model}="ST336", NAME="boot%n"
+BUS=="scsi", SYSFS{vendor}=="IBM", SYSFS{model}=="ST336", NAME="boot%n"
# sound card with PCI bus id 00:0b.0 to be called dsp
-BUS="pci", ID="00:0b.0", NAME="dsp"
+BUS=="pci", ID=="00:0b.0", NAME="dsp"
# USB mouse at third port of the second hub to be called mouse1
-BUS="usb", PLACE="2.3", NAME="mouse1"
+BUS=="usb", ID=="2.3", NAME="mouse1"
# ttyUSB1 should always be called pda with two additional symlinks
-KERNEL="ttyUSB1", NAME="pda", SYMLINK="palmtop handheld"
+KERNEL=="ttyUSB1", NAME="pda", SYMLINK="palmtop handheld"
# multiple USB webcams with symlinks to be called webcam0, webcam1, ...
-BUS="usb", SYSFS{model}="XV3", NAME="video%n", SYMLINK="webcam%n"
-
-# grouping of optical drives from multiple kernel subsystems
-KERNEL="sr*", NAME="%k", SYMLINK="cdrom%e"
-KERNEL="scd*", NAME="%k", SYMLINK="cdrom%e"
-KERNEL="pcd*", NAME="%k", SYMLINK="cdrom%e"
-KERNEL="hd[a-z]", PROGRAM="/bin/cat /proc/ide/%k/media", RESULT="cdrom",
- NAME="%k", SYMLINK="cdrom%e"
-
-.fi
-.P
-The permissions and ownership of the created device file is read from
-the files located in the
-.I /etc/udev/permissions.d/
-directory, or at the location specified by the
-.I udev_permission
-value in the
-.I /etc/udev/udev.conf
-file.
-.br
-Every line lists a device name followed by owner, group and permission
-mode. All values are separated by colons. The name field may contain a
-pattern to apply the values to a whole class of devices.
-.sp
-.RI "A sample " udev.permissions " might look like this:"
-.sp
-.nf
-#name:user:group:mode
-input/*:root:root:644
-ttyUSB1:0:8:0660
-video*:root:video:0660
-dsp1:::0666
+BUS=="usb", SYSFS{model}=="XV3", NAME=="video%n", SYMLINK="webcam%n"
.fi
.P
A number of different fields in the above configuration files support a simple
.TP
.B [ ]
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
+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 character not enclosed is matched.
+following the '[' is a '!', any characters not enclosed are matched.
.P
After device node creation, removal, or network device renaming,
.B udev
-executes the programs in the directory tree under
-.IR /etc/dev.d/ .
-The name of a program must end with
-.I .dev
-suffix, to be recognized.
+executes the programs specified by the
+.B RUN
+key.
.br
-In addition to the hotplug environment variables,
+In addition to the kernel provided hotplug environment variables,
+.B UDEV_LOG
+is set and contains the numerical priority value, if udev is configured to use
+.BR syslog (3).
+Executed programs may want to follow that setting.
.B DEVNAME
is exported to make the name of the created node, or the name the network
-device is renamed to, available to the executed program. The programs in every
-directory are sorted in lexical order, while the directories are searched in
-the following order:
-.sp
-.nf
-/etc/dev.d/$(DEVNAME)/*.dev
-/etc/dev.d/$(SUBSYSTEM)/*.dev
-/etc/dev.d/default/*.dev
-.fi
+device is renamed to, available to the executed programs.
+.SH "ENVIRONMENT"
+.P
+The following variables are read from the environment:
+.TP
+.B ACTION
+.IR add " or " remove
+signifies the addition or the removal of a device.
+.TP
+.B DEVPATH
+The sysfs devpath of the device without the mountpoint but a leading slash.
+.TP
+.B SUBSYSTEM
+The subsystem the device belongs to. Alternatively the subsystem may
+be passed as the first argument.
+.TP
+.B UDEV_CONFIG_FILE
+Overrides the default location of the
+.B udev
+config file.
+.TP
+.B UDEV_LOG
+Overrides the log priority specified in the config file.
+.TP
+.B UDEV_RUN
+If set to "0", it disables the execution of programs added by rules.
.SH "FILES"
.nf
/sbin/udev udev program
/etc/udev/* udev config files
-/etc/hotplug.d/default/udev.hotplug hotplug symlink to udev program
-/etc/dev.d/* programs invoked by udev
.fi
-.LP
.SH "SEE ALSO"
.BR udevinfo (8),
.BR udevd (8),
-.BR hotplug (8)
.PP
-The
+.B Web resources:
+.nf
+.I http://www.kernel.org/pub/linux/utils/kernel/hotplug/udev.html
.I http://linux\-hotplug.sourceforge.net/
-web site.
+.fi
.SH AUTHORS
.B udev
was developed by Greg Kroah-Hartman <greg@kroah.com> with much help from
~ianmdlvl / elogind.git / blobdiff