.SH NAME
udev \- Linux configurable dynamic device naming support
.SH SYNOPSIS
-.BI udev " hotplug-subsystem"
+.BI udev
.SH "DESCRIPTION"
.B udev
provides a dynamic device directory containing only the files for actually
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
.IR /etc/udev/rules.d/ .
.TP
.B udev_log
-The switch to enable/disable logging of udev information
+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 .
+.IR err .
.P
.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"
+# Where in the filesystem to place the device nodes
+udev_root="@udevdir@"
-# udev_db - The name and location of the udev database
-udev_db="/udev/.udevdb"
+# The name and location of the udev database.
+udev_db="@udevdir@/.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/"
+# 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"
+# 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
.B SUBSYSTEM
Match the kernel subsystem name.
.TP
+.B ACTION
+Match the kernel action name.
+.TP
.B DRIVER
Match the kernel driver name.
.TP
should be renamed to.
.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 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 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.
+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 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
-will be the last rule applied. No later rules will have any effect.
+stops further rules application. No later rules will have any effect.
.sp
-.B OPTIONS
.B ignore_device
-will ignore this device. No node will be created.
+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.
.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
.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
# 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
A number of different fields in the above configuration files support a simple
.I .dev
to be recognized.
.br
-In addition to the hotplug environment variables,
+In addition to the kernel provided 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.
+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
.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.
+.TP
.B UDEV_NO_DEVD
The default behavior of
.B udev
.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
.SH "SEE ALSO"
.PP
.B Web resources:
.nf
-.I http://linux\-hotplug.sourceforge.net/
.I http://www.kernel.org/pub/linux/utils/kernel/hotplug/udev.html
+.I http://linux\-hotplug.sourceforge.net/
.fi
.SH AUTHORS
.B udev
~ianmdlvl / elogind.git / blobdiff