1SYSTEMD.DEVICE(5) systemd.device SYSTEMD.DEVICE(5)
2
6 systemd.device - Device unit configuration
7
9 device.device
10
12 A unit configuration file whose name ends in ".device" encodes
13 information about a device unit as exposed in the sysfs/udev(7) device
14 tree.
15 This unit type has no specific options. See systemd.unit(5) for the
17 common options of all unit configuration files. The common
18 configuration items are configured in the generic [Unit] and [Install]
19 sections. A separate [Device] section does not exist, since no
20 device-specific options may be configured.
21 systemd will dynamically create device units for all kernel devices
23 that are marked with the "systemd" udev tag (by default all block and
24 network devices, and a few others). This may be used to define
25 dependencies between devices and other units. To tag a udev device, use
26 "TAG+="systemd"" in the udev rules file, see udev(7) for details.
27 Device units are named after the /sys and /dev paths they control.
29 Example: the device /dev/sda5 is exposed in systemd as dev-sda5.device.
30 For details about the escaping logic used to convert a file system path
31 to a unit name see systemd.unit(5).
32 Device units will be reloaded by systemd whenever the corresponding
34 device generates a "changed" event. Other units can use
35 ReloadPropagatedFrom= to react to that event.
36
38 Implicit Dependencies
39 Many unit types automatically acquire dependencies on device units of
40 devices they require. For example, .socket unit acquire dependencies on
41 the device units of the network interface specified in BindToDevice=.
42 Similar, swap and mount units acquire dependencies on the units
43 encapsulating their backing block devices.
44 Default Dependencies
46 There are no default dependencies for device units.
47
49 Unit settings of device units may either be configured via unit files,
50 or directly from the udev database. The following udev device
51 properties are understood by the service manager:
52 SYSTEMD_WANTS=, SYSTEMD_USER_WANTS=
54 Adds dependencies of type Wants= from the device unit to the
55 specified units. SYSTEMD_WANTS= is read by the system service
56 manager, SYSTEMD_USER_WANTS= by user service manager instances.
57 These properties may be used to activate arbitrary units when a
58 specific device becomes available.
59 Note that this and the other udev device properties are not taken
61 into account unless the device is tagged with the "systemd" tag in
62 the udev database, because otherwise the device is not exposed as a
63 systemd unit (see above).
64 Note that systemd will only act on Wants= dependencies when a
66 device first becomes active. It will not act on them if they are
67 added to devices that are already active. Use SYSTEMD_READY= (see
68 below) to configure when a udev device shall be considered active,
69 and thus when to trigger the dependencies.
70 The specified property value should be a space-separated list of
72 valid unit names. If a unit template name is specified (that is, a
73 unit name containing an "@" character indicating a unit name to use
74 for multiple instantiation, but with an empty instance name
75 following the "@"), it will be automatically instantiated by the
76 device's "sysfs" path (that is: the path is escaped and inserted as
77 instance name into the template unit name). This is useful in order
78 to instantiate a specific template unit once for each device that
79 appears and matches specific properties.
80 SYSTEMD_ALIAS=
82 Adds an additional alias name to the device unit. This must be an
83 absolute path that is automatically transformed into a unit name.
84 (See above.)
85 SYSTEMD_READY=
87 If set to 0, systemd will consider this device unplugged even if it
88 shows up in the udev tree. If this property is unset or set to 1,
89 the device will be considered plugged if it is visible in the udev
90 tree.
91 This option is useful for devices that initially show up in an
93 uninitialized state in the tree, and for which a "changed" event is
94 generated the moment they are fully set up. Note that
95 SYSTEMD_WANTS= (see above) is not acted on as long as
96 SYSTEMD_READY=0 is set for a device.
97 ID_MODEL_FROM_DATABASE=, ID_MODEL=
99 If set, this property is used as description string for the device
100 unit.
101
103 systemd(1), systemctl(1), systemd.unit(5), udev(7),
104 systemd.directives(7)
105systemd 246 SYSTEMD.DEVICE(5)