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 are:
+.TP
+.B UDEV_CONFIG_FILE
+Overrides the default location of the
+.B udev
+config file.
+.TP
+.B UDEV_NO_SLEEP
+The default behavior of
+.B udev
+is to wait until all the sysfs files of the device chain are populated. If set
+.B udev
+will continue, regardless of the state of the device representation.
.SH "DESCRIPTION"
.B udev
creates or removes device node files usually located in the /dev directory.
-Its goal is to provide a dynamic device directory that contains only the files
-for devices that are actually present.
+It provides a dynamic device directory that contains only the files for
+devices that are actually present.
.P
As part of the
.B hotplug
.B udev
reads the sysfs directory of the given device to collect device attributes
like label, serial number or bus device number.
-These attributes are treated as a key
-to determine a unique name for device file creation.
+These attributes may used as keys to determine a
+unique name for device file creation.
.B udev
maintains a database for devices present on the system.
.br
On device removal,
.B udev
-queries the internal database for the name of the device file to be deleted.
+queries its database for the name of the device file to be deleted.
.SH "CONFIGURATION"
-All udev configuration files consist of a set of lines of text. All empty
+All
+.B udev
+configuration files consist of a set of lines of text. All empty
lines, and lines beginning with a '#' will be ignored.
.P
.B udev
expects its main configuration file at
-.I /etc/udev/udev.conf.
+.IR /etc/udev/udev.conf .
The file consists of a set of variables and values that allow the user to
override default udev values. The current set of variables that can be
overridden in this file is:
.B udev_root
This is the where in the filesystem to place the device nodes. The default
value for this is
-.I /udev/
+.IR /udev/ .
.TP
.B udev_db
The name and location of the udev database. The default value for this is
-.I /udev/.udev.tdb
+.IR /udev/.udev.tdb .
.TP
.B udev_rules
This is the location of the udev rules file. The default value for this is
-.I /etc/udev/udev.rules
+.IR /etc/udev/udev.rules .
+If a directory is specified, the whole directory is
+scanned for files ending with
+.I .rules
+and all rule files are read in lexical order.
.TP
.B udev_permissions
-This is the location of the udev permission file. The default value for this is
-.I /etc/udev/udev.permissions
+This is the location of the udev permission file. The default value for this is
+.IR /etc/udev/udev.permissions .
+If a directory is specified, the whole directory is scanned for files ending with
+.I .permissions
+and all permission files are read in lexical order.
+.TP
+.B udev_log
+If you want udev to log some information to the syslog for every node created or
+removed. The default value for this is
+.IR yes .
.TP
.B default_mode
This is the default mode for all nodes that have no explicit match in the
permissions file. The default value for this is
-.I 0666
+.IR 0666 .
+.TP
+.B default_owner
+This is the default owner for all nodes that have no explicit match in the
+permissions file. The default value for this is
+.IR root .
+.TP
+.B default_group
+This is the default group for all nodes that have no explicit match in the
+permissions file. The default value for this is
+.IR root .
.br
.P
-A sample \fIudev.conf\fP might look like this:
+.RI "A sample " udev.conf " might look like this:
.sp
.nf
# udev_root - where in the filesystem to place the device nodes
# udev_db - The name and location of the udev database.
udev_db="/udev/.udev.tdb"
-# udev_rules - The name and location of the udev rules file
-udev_rules="/etc/udev/udev.rules"
+# udev_rules - The location of the directory where to look for files
+ which names ending with .rules
+udev_rules="/etc/udev/"
# udev_permissions - The name and location of the udev permission file
udev_permissions="/etc/udev/udev.permissions"
-# default_mode - set the default mode for all nodes that have no
+# udev_log - set to "yes" if you want logging, else "no"
+udev_log="yes"
+
+# default_mode - set the default mode for all nodes that have no
# explicit match in the permissions file
default_mode="0666"
+
+# default_owner - set the default owner for all nodes that have no
+# explicit match in the permissions file
+default_owner="root"
+
+# default_group - set the default group for all nodes that have no
+# explicit match in the permissions file
+default_group="root"
.fi
.P
The rules for udev to use when naming devices may specified at
.I /etc/udev/udev.rules
-or specified by the
+or specified by the
.I udev_rules
-value in the
+value in the
.I /etc/udev/udev.conf
file.
.P
-Every line in the rules file define the mapping between device attributes and
-the device file name. It starts with a keyword defining the method used to
-match, followed by one ore more keys to compare and the filename for the
-device. If no matching configuration is found, the default kernel device name
-is used.
+Every line in the rules file defines the mapping between device attributes
+and the device file name. One ore more keys are specified to match a rule
+with the current device. If all keys are matching, the rule will be applied
+and the name is used for the device node.
+.br
+If no matching rule is found, the default kernel device name is used.
.P
-The line format is:
-.RS
+Every rule consists of a list a comma separated fields:
.sp
-.I method, key,[key,...] name
+.IR "key " ,[ "key " ,...] " name " [, " symlink" ]
.sp
-.RE
-where valid methods with corresponding keys are:
+where possible fields are:
.TP
-.B CALLOUT
-calling external program, that returns a string to match
-.br
-keys: \fBBUS\fP, \fBPROGRAM\fP, \fBID\fP
+.B BUS
+Match the bus type of the device.
+(The sysfs device bus must be able to be determined by a "device" symlink.)
+.TP
+.B KERNEL
+Match the kernel device 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
-.B LABEL
-device label or serial number, like USB serial number, SCSI UUID or
-file system label
+.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 in order to match the rule.
.br
-keys: \fBBUS\fP, \fIsysfs_attribute\fP
+Trailing whitespace characters in the sysfs attribute value are ignored, if
+the key doesn't have any trailing whitespace characters by itself.
.TP
-.B NUMBER
-device number on the bus, like PCI bus id
+.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.
.br
-keys: \fBBUS\fP, \fBID\fP
+The string returned by the program may additionally matched with the
+.B RESULT
+key.
+.TP
+.B RESULT
+Match the returned string of the last
+.B PROGRAM
+call. This key may used in any following rule after a
+.B PROGRAM
+call.
.TP
-.B TOPOLOGY
-device position on bus, like physical port of USB device
+.B NAME
+The name of the node to be created.
.br
-keys: \fBBUS\fP, \fBPLACE\fP
+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.
.TP
-.B REPLACE
-string replacement of the kernel device name
+.B SYMLINK
+The name of a symlink targeting the node. Multiple symlinks may be
+specified by separating the names by the space character.
.br
-key: \fBKERNEL_NAME\fP
-.P
-The methods are applied in the following order:
-.B CALLOUT
-,
-.B LABEL
-,
-.B NUMBER
-,
-.B TOPOLOGY
-,
-.B REPLACE
+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.
.P
-The
-.B NAME
-and
-.B PROGRAM
-fields support simple printf-like string subtitution:
-.RS
+.RB "The " NAME " ," SYMLINK " and " PROGRAM
+fields support simple printf-like string substitution:
.TP
.B %n
-the "kernel number" of the device
-for example, 'sda3' has a "kernel number" of '3'
+The "kernel number" of the device.
+For example, 'sda3' has a "kernel number" of '3'.
+.TP
+.B %k
+The "kernel name" for the device.
.TP
.B %M
-the kernel major number for the device
+The kernel major number for the device.
.TP
.B %m
-the kernel minor number for the device
+The kernel minor number for the device.
.TP
.B %b
-the bus id for the device
+The bus id for the device.
.TP
.B %c
-the CALLOUT program returned string
-(this does not work within the PROGRAM field for the obvious reason.)
-.TP
-.B %D
-Use the devfs style disk name for this device.
-For partitions, this will result in 'part%n'
-If this is not a partition, it will result in 'disk'
-.RE
+The
+.B PROGRAM
+returned string.
+(This does not work within the
+.B PROGRAM
+field for the obvious reason.)
+.br
+A single part of the string, separated by the space character
+my be selected by specifying the part number as a attribute:
+.BI %c{ part }
+.TP
+.BI %s{ filename }
+The content of a sysfs attribute.
+.TP
+.B %%
+The '%' character itself.
+.P
+The count of charcters 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
-A sample \fIudev.rules\fP might look like this:
+.RI "A sample " udev.rules " might look like this:"
.sp
.nf
# if /sbin/scsi_id returns "OEM 0815" device will be called disk1
-CALLOUT, BUS="scsi", PROGRAM="/sbin/scsi_id", ID="OEM 0815", NAME="disk1"
+BUS="scsi", PROGRAM="/sbin/scsi_id", RESULT="OEM 0815", NAME="disk1"
# USB printer to be called lp_color
-LABEL, BUS="usb", serial="W09090207101241330", NAME="lp_color"
+BUS="usb", SYSFS{serial}="W09090207101241330", NAME="lp_color"
+
+# SCSI disk with a specific vendor and model number is to be called boot
+BUS="scsi", SYSFS{vendor}="IBM", SYSFS{model}="ST336", NAME="boot%n"
# sound card with PCI bus id 00:0b.0 to be called dsp
-NUMBER, 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
-TOPOLOGY, BUS="usb", PLACE="2.3", NAME="mouse1"
+BUS="usb", PLACE="2.3", NAME="mouse1"
-# ttyUSB1 should always be called pda
-REPLACE, KERNEL="ttyUSB1", NAME="pda"
+# ttyUSB1 should always be called pda with two additional symlinks
+KERNEL="ttyUSB1", NAME="pda", SYMLINK="palmtop handheld"
-# USB webcams to be called webcam0, webcam1, ...
-LABEL, BUS="usb", model="WebCam Version 3", NAME="webcam%n"
+# multiple USB webcams with symlinks to be called webcam0, webcam1, ...
+BUS="usb", SYSFS{model}="XV3", NAME="video%n", SYMLINK="webcam%n"
.fi
.P
Permissions and ownership for the created device files may specified at
.I /etc/udev/udev.permissions
-or specified by the
+or specified by the
.I udev_permission
-value in the
+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
-wildcard to apply the values to a whole class of devices.
-.br
-If
-.B udev
-was built using klibc or is used before the user database is accessible (e.g.
-.B initrd
-), only numeric owner and group values may be used.
+pattern to apply the values to a whole class of devices.
.sp
-A sample \fIudev.permissions\fP might look like this:
+.RI "A sample " udev.permissions " might look like this:"
.sp
.nf
#name:user:group:mode
dsp1:::0666
.fi
.P
+The value
+.I $local
+can be substituted for a specific username. In that case, udev will determine
+the current local user at the time of device node creation and substitute
+that username as the owner of the new device node. This is useful, for
+example, to let hot-plugged devices, such as cameras, be owned by the user at
+the current console. Note that if no user is currently logged in, or if udev
+otherwise fails to determine a current user, the
+.I default_owner
+value is used in lieu.
+.P
A number of different fields in the above configuration files support a simple
-form of wildcard matching. This form is based on the fnmatch(3) style, and
-supports the following fields:
-.RS
+form of shell style pattern matching. It supports the following pattern characters:
.TP
.B *
Matches zero, one, or more characters.
.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
-the range of all digits, the pattern [0-9] would be used.
-.RE
+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 '!' then any character not enclosed is matched.
.SH "FILES"
.nf
-.ft B
-.ft
/sbin/udev udev program
/etc/udev/* udev config files
/etc/hotplug.d/default/udev.hotplug hotplug symlink to udev program
.fi
.LP
.SH "SEE ALSO"
+.BR udevinfo (8),
+.BR udevd (8),
.BR hotplug (8)
.PP
The
-.I http://linux-hotplug.sourceforge.net/
+.I http://linux\-hotplug.sourceforge.net/
web site.
.SH AUTHORS
.B udev
~ianmdlvl / elogind.git / blobdiff