1 .TH UDEV 8 "October 2003" "" "Linux Administrator's Manual"
3 udev \- Linux configurable dynamic device naming support
5 .BI udev " hotplug-subsystem"
8 creates or removes device node files usually located in the /dev directory.
9 Its goal is to provide a dynamic device directory that contains only the files
10 for devices that are actually present.
16 is executed if a kernel device is added or removed from the system.
19 reads the sysfs directory of the given device to collect device attributes
20 like label, serial number or bus device number.
21 These attributes are treated as a key
22 to determine a unique name for device file creation.
24 maintains a database for devices present on the system.
28 queries the internal database for the name of the device file to be deleted.
32 configuration files consist of a set of lines of text. All empty
33 lines, and lines beginning with a '#' will be ignored.
37 expects its main configuration file at
38 .I /etc/udev/udev.conf.
39 The file consists of a set of variables and values that allow the user to
40 override default udev values. The current set of variables that can be
41 overridden in this file is:
44 This is the where in the filesystem to place the device nodes. The default
49 The name and location of the udev database. The default value for this is
53 This is the location of the udev rules file. The default value for this is
54 .I /etc/udev/udev.rules
57 This is the location of the udev permission file. The default value for this is
58 .I /etc/udev/udev.permissions
61 This is the default mode for all nodes that have no explicit match in the
62 permissions file. The default value for this is
66 .RI "A sample " udev.conf " might look like this:
69 # udev_root - where in the filesystem to place the device nodes
72 # udev_db - The name and location of the udev database.
73 udev_db="/udev/.udev.tdb"
75 # udev_rules - The name and location of the udev rules file
76 udev_rules="/etc/udev/udev.rules"
78 # udev_permissions - The name and location of the udev permission file
79 udev_permissions="/etc/udev/udev.permissions"
81 # default_mode - set the default mode for all nodes that have no
82 # explicit match in the permissions file
86 The rules for udev to use when naming devices may specified at
87 .I /etc/udev/udev.rules
91 .I /etc/udev/udev.conf
94 Every line in the rules file define the mapping between device attributes and
95 the device file name. It starts with a keyword defining the method used to
96 match, followed by one ore more keys to compare and the filename for the
97 device. One ore more optional symlinks targeting the node may be specified.
99 If no matching configuration is found, the default kernel device name
104 .I method, key,[key,...] name [, symlink]
106 where valid methods with corresponding keys are:
109 calling external program, that returns a string to match
111 .RB "keys: " BUS ", " PROGRAM ", " ID
114 device label or serial number, like USB serial number, SCSI UUID or
117 .RB "keys: " BUS ", " SYSFS_
120 device number on the bus, like PCI bus id
122 .RB "keys: " BUS ", " ID
125 device position on bus, like physical port of USB device
127 .RB "keys: " BUS ", " PLACE
130 string replacement of the kernel device name
134 The methods are applied in the following order:
135 .BR CALLOUT ", " LABEL ", " NUMBER ", " TOPOLOGY ", " REPLACE "."
137 .RB "The " NAME " ," SYMLINK " and " PROGRAM
138 fields support simple printf-like string substitution:
141 The "kernel number" of the device.
142 for example, 'sda3' has a "kernel number" of '3'
145 The kernel major number for the device.
148 The kernel minor number for the device.
151 The bus id for the device.
154 The CALLOUT program returned string.
155 (This does not work within the PROGRAM field for the obvious reason.)
158 Use the devfs style disk name for this device.
159 For partitions, this will result in 'part%n'
160 If this is not a partition, it will result in 'disc'.
162 .RI "A sample " udev.rules " might look like this:"
165 # if /sbin/scsi_id returns "OEM 0815" device will be called disk1
166 CALLOUT, BUS="scsi", PROGRAM="/sbin/scsi_id", ID="OEM 0815", NAME="disk1"
168 # USB printer to be called lp_color
169 LABEL, BUS="usb", SYSFS_serial="W09090207101241330", NAME="lp_color"
171 # sound card with PCI bus id 00:0b.0 to be called dsp
172 NUMBER, BUS="pci", ID="00:0b.0", NAME="dsp"
174 # USB mouse at third port of the second hub to be called mouse1
175 TOPOLOGY, BUS="usb", PLACE="2.3", NAME="mouse1"
177 # ttyUSB1 should always be called pda with two additional symlinks
178 REPLACE, KERNEL="ttyUSB1", NAME="pda", SYMLINK="palmtop handheld"
180 # multiple USB webcams with symlinks to be called webcam0, webcam1, ...
181 LABEL, BUS="usb", SYSFS_model="XV3", NAME="video%n", SYMLINK="webcam%n"
184 Permissions and ownership for the created device files may specified at
185 .I /etc/udev/udev.permissions
189 .I /etc/udev/udev.conf
192 Every line lists a device name followed by owner, group and permission
193 mode. All values are separated by colons. The name field may contain a
194 pattern to apply the values to a whole class of devices.
198 was built using klibc or is used before the user database is accessible (e.g.
199 .BR initrd "(4)), only numeric owner and group values may be used."
201 .RI "A sample " udev.permissions " might look like this:"
204 #name:user:group:mode
205 input/*:root:root:644
207 video*:root:video:0660
211 A number of different fields in the above configuration files support a simple
212 form of shell style pattern matching. It supports the following pattern characters:
215 Matches zero, one, or more characters.
218 Matches any single character, but does not match zero characters.
221 Matches any single character specified within the brackets. For example, the
222 pattern string "tty[SR]" would match either "ttyS" or "ttyR". Ranges are also
223 supported within this match with the '-' character. For example, to match on
224 the range of all digits, the pattern [0-9] would be used. If the first character
225 following the '[' is a '!' then any character not enclosed is matched.
228 /sbin/udev udev program
229 /etc/udev/* udev config files
230 /etc/hotplug.d/default/udev.hotplug hotplug symlink to udev program
237 .I http://linux-hotplug.sourceforge.net/
241 was developed by Greg Kroah-Hartman <greg@kroah.com> with much help from
242 Dan Stekloff <dsteklof@us.ibm.com>, Kay Sievers <kay.sievers@vrfy.org>, and