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.
31 expects its configuration at
32 .I /etc/udev/udev.config.
33 The file consists of a set of lines. All empty lines and
34 lines beginning with a '#' will be ignored.
36 Every line defines the mapping between device attributes and the device file
37 name. It starts with a keyword defining the method used to match, followed by
38 one ore more keys to compare and the filename for the device. If no matching
39 configuration is found, the default kernel device name is used.
44 .I method, key,[key,...] name
47 where valid methods with corresponding keys are:
50 calling external program, that returns a string to match
52 keys: \fBBUS\fP, \fBPROGRAM\fP, \fBID\fP
55 device label or serial number, like USB serial number, SCSI UUID or
58 keys: \fBBUS\fP, \fIsysfs_attribute\fP
61 device number on the bus, like PCI bus id
63 keys: \fBBUS\fP, \fBID\fP
66 device position on bus, like physical port of USB device
68 keys: \fBBUS\fP, \fBPLACE\fP
71 string replacement of the kernel device name
73 key: \fBKERNEL_NAME\fP
75 The methods are applied in the following order:
90 fields support simple printf-like string subtitution:
94 the "kernel number" of the device
95 for example, 'sda3' has a "kernel number" of '3'
98 the kernel major number for the device
101 the kernel minor number for the device
104 the bus id for the device
107 the CALLOUT program returned string
108 (this does not work within the PROGRAM field for the obvious reason.)
111 A sample \fIudev.conf\fP might look like this:
114 # if /sbin/scsi_id returns "OEM 0815" device will be called disk1
115 CALLOUT, BUS="scsi", PROGRAM="/sbin/scsi_id", ID="OEM 0815", NAME="disk1"
117 # USB printer to be called lp_color
118 LABEL, BUS="usb", serial="W09090207101241330", NAME="lp_color"
120 # sound card with PCI bus id 00:0b.0 to be called dsp
121 NUMBER, BUS="pci", ID="00:0b.0", NAME="dsp"
123 # USB mouse at third port of the second hub to be called mouse1
124 TOPOLOGY, BUS="usb", PLACE="2.3", NAME="mouse1"
126 # ttyUSB1 should always be called pda
127 REPLACE, KERNEL="ttyUSB1", NAME="pda"
129 # USB webcams to be called webcam0, webcam1, ...
130 LABEL, BUS="usb", model="WebCam Version 3", NAME="webcam%n"
133 Permissions and ownership for the created device files may specified at
134 .I /etc/udev/udev.permissions.
135 The file consists of a set of lines. All empty lines and
136 lines beginning with a '#' will be ignored.
138 Every line lists a device name followed by owner, group and permission
139 mode. All values are separated by colons. The name field may end with a
140 wildcard to apply the values to a whole class of devices.
144 was built using klibc or is used before the user database is accessible (e.g.
146 ), only numeric owner and group values may be used.
148 A sample \fIudev.permissions\fP might look like this:
151 #name:user:group:mode
152 input/*:root:root:644
154 video*:root:video:0660
161 /sbin/udev udev program
162 /etc/udev/* udev config and database files
163 /etc/hotplug.d/default/udev.hotplug hotplug symlink to udev program
170 .I http://linux-hotplug.sourceforge.net/
174 was developed by Greg Kroah-Hartman <greg@kroah.com> with much help from
175 Dan Stekloff <dsteklof@us.ibm.com> and many others.