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_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.
-.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.
.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
.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 .
.B udev_root
Indicates where to place the device nodes in the filesystem. The default
value is
-.IR @udevdir@ .
+.IR @udevdir@/ .
.TP
.B udev_db
The name and location of the udev database. The default value is
-.IR @udevdir@/.udev.tdb .
+.IR @udevdir@/.udevdb .
.TP
.B udev_rules
The name of the udev rules file or directory to look for files with the suffix
.IR .rules .
All rule files are read in lexical order. The default value is
-.IR /etc/udev/udev.rules .
-.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/udev.permissions .
+.IR /etc/udev/rules.d/ .
.TP
.B udev_log
-The switch, if udev logs some information for every device handled.
+The switch to enable/disable logging of udev information
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 .
+The default mode for all nodes where no explicit value is given by a rule.
+The default value is
+.IR 0600 .
.TP
.B default_owner
-The default owner for all nodes not explicitely matching in the permissions
-file. The default value is
+The default owner for all nodes where no explicit value is given by a rule.
+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
+The default group for all nodes where no explicitly value is given by a rule.
+The default value is
.IR root .
.br
.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="@udevdir@"
+udev_root="/udev"
# udev_db - The name and location of the udev database
-udev_db="@udevdir@/.udev.tdb"
+udev_db="/udev/.udevdb"
# 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/"
-# udev_permissions - The name of the udev permission file or directry to look
- for files with the suffix .permissions
-udev_permissions="/etc/udev/udev.permissions"
-
# 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 - set the default mode for all nodes that have no
+# permissions specified
default_mode="0666"
-# default_owner - set the default owner for all nodes not
-# explicitely matching in the permissions file
+# default_owner - set the default owner for all nodes that have no
+# permissions specified
default_owner="root"
-# default_group - set the default group for all nodes not
-# explicitely matching in the permissions file
+# default_group - set the default group for all nodes that have no
+# permissions specified
default_group="root"
.fi
.P
-The rules for udev to use when naming devices may specified in
-.I /etc/udev/udev.rules
-or by 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
value in the
.I /etc/udev/udev.conf
file.
-.P
+.br
Every line in the rules file defines the mapping between device attributes
and the device name. One or more keys are specified to match a rule with
the current device. If all keys are matching, the rule will be applied and
.B KERNEL
Match the kernel device name.
.TP
+.B SUBSYSTEM
+Match the kernel subsystem name.
+.TP
+.B DRIVER
+Match the kernel driver name.
+.TP
.B ID
Match the device number on the bus, like PCI bus id.
.TP
.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
+or file system label. 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
.br
If given with the attribute
.BR NAME{ all_partitions }
-it will create all 15 partitions of a blockdevice.
+.B udev
+will create device nodes for all 15 partitions of a blockdevice.
This may be useful for removable media devices.
+.br
+If given with the attribute
+.BR NAME{ ignore_remove }
+.B udev
+will ignore any later remove event for this device.
+This may be useful as a workaround for broken device drivers.
+.sp
+Multiple attributes may be separated by comma.
.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.
+values are 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
+the rule will not be applied immediately, 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.
.TP
.B OWNER, GROUP, MODE
-The permissions for this device. Every specified value overwrites the value
-given in the permissions file.
+The permissions for this device. Every specified value overwrites the default
+value specified in the config file.
.P
.RB "The " NAME " ," SYMLINK " and " PROGRAM
-fields support simple printf-like string substitution:
+fields support simple printf-like string substitutions:
.TP
.B %n
The "kernel number" of the device.
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
.BI %s{ filename }
The content of a sysfs attribute.
.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.
+.TP
.B %%
The '%' character itself.
.P
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
+# 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
# 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
-Permissions and ownership for the created device files may specified in
-.I /etc/udev/udev.permissions
-or 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
-.fi
-.P
-The value
-.I $local
-can be used instead of a specific username. In that case, udev will determine
-the current local user at the time of device node creation and substitute
-that username as the owner of the new device node. This is useful, for
-example, to let hot-plugged devices, such as cameras, be owned by the user at
-the current console. Note that if no user is currently logged in, or if udev
-otherwise fails to determine a current user, the
-.I default_owner
-value is used in lieu.
-.P
A number of different fields in the above configuration files support a simple
form of shell style pattern matching. It supports the following pattern characters:
.TP
.TP
.B [ ]
Matches any single character specified within the brackets. For example, the
-pattern string "tty[SR]" would match either "ttyS" or "ttyR". Ranges are also
-supported within this match with the '\-' character. For example, to match on
+pattern string "tty[SR]" would match either "ttyS" or "ttyR". Ranges are also
+supported within this match with the '\-' character. For example, to match on
the range of all digits, the pattern [0\-9] would be used. If the first character
-following the '[' is a '!', any character not enclosed is matched.
+following the '[' is a '!', any characters not enclosed are matched.
.P
After device node creation, removal, or network device renaming,
.B udev
-executes the programs in the directory tree under
+executes the programs located in the directory tree under
.IR /etc/dev.d/ .
-The name of a program must end with
+The name of a program must have the suffix
.I .dev
-suffix, to be recognized.
+to be recognized.
.br
In addition to the hotplug environment variables,
+.B UDEV_LOG
+is set if udev is configured to use the syslog facility. Executed programs may
+want to follow that setting.
.B DEVNAME
is exported to make the name of the created node, or the name the network
device is renamed to, available to the executed program. The programs in every
/etc/dev.d/$(SUBSYSTEM)/*.dev
/etc/dev.d/default/*.dev
.fi
+.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_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.
.SH "FILES"
.nf
/sbin/udev udev program
/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://linux\-hotplug.sourceforge.net/
-web site.
+.I http://www.kernel.org/pub/linux/utils/kernel/hotplug/udev.html
+.fi
.SH AUTHORS
.B udev
was developed by Greg Kroah-Hartman <greg@kroah.com> with much help from
~ianmdlvl / elogind.git / blobdiff