1SYSTEMD.DEVICE(5)               systemd.device               SYSTEMD.DEVICE(5)
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NAME

6       systemd.device - Device unit configuration
7

SYNOPSIS

9       device.device
10

DESCRIPTION

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. This may be used to define dependencies between devices and other
15       units.
16
17       This unit type has no specific options. See systemd.unit(5) for the
18       common options of all unit configuration files. The common
19       configuration items are configured in the generic [Unit] and [Install]
20       sections. A separate [Device] section does not exist, since no
21       device-specific options may be configured.
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23       systemd will dynamically create device units for all kernel devices
24       that are marked with the "systemd" udev tag (by default all block and
25       network devices, and a few others). Note that if systemd-udevd.service
26       is not running, no device units will be available (for example in a
27       typical container).
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29       Device units are named after the /sys/ and /dev/ paths they control.
30       Example: the device /dev/sda5 is exposed in systemd as dev-sda5.device.
31       For details about the escaping logic used to convert a file system path
32       to a unit name see systemd.unit(5).
33
34       To tag a udev device, use "TAG+="systemd"" in the udev rules file, see
35       udev(7) for details.
36
37       Device units will be reloaded by systemd whenever the corresponding
38       device generates a "changed" event. Other units can use
39       ReloadPropagatedFrom= to react to that event.
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AUTOMATIC DEPENDENCIES

42   Implicit Dependencies
43       Many unit types automatically acquire dependencies on device units of
44       devices they require. For example, .socket unit acquire dependencies on
45       the device units of the network interface specified in BindToDevice=.
46       Similar, swap and mount units acquire dependencies on the units
47       encapsulating their backing block devices.
48
49   Default Dependencies
50       There are no default dependencies for device units.
51

THE UDEV DATABASE

53       Unit settings of device units may either be configured via unit files,
54       or directly from the udev database. The following udev device
55       properties are understood by the service manager:
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57       SYSTEMD_WANTS=, SYSTEMD_USER_WANTS=
58           Adds dependencies of type Wants= from the device unit to the
59           specified units.  SYSTEMD_WANTS= is read by the system service
60           manager, SYSTEMD_USER_WANTS= by user service manager instances.
61           These properties may be used to activate arbitrary units when a
62           specific device becomes available.
63
64           Note that this and the other udev device properties are not taken
65           into account unless the device is tagged with the "systemd" tag in
66           the udev database, because otherwise the device is not exposed as a
67           systemd unit (see above).
68
69           Note that systemd will only act on Wants= dependencies when a
70           device first becomes active. It will not act on them if they are
71           added to devices that are already active. Use SYSTEMD_READY= (see
72           below) to configure when a udev device shall be considered active,
73           and thus when to trigger the dependencies.
74
75           The specified property value should be a space-separated list of
76           valid unit names. If a unit template name is specified (that is, a
77           unit name containing an "@" character indicating a unit name to use
78           for multiple instantiation, but with an empty instance name
79           following the "@"), it will be automatically instantiated by the
80           device's "sysfs" path (that is: the path is escaped and inserted as
81           instance name into the template unit name). This is useful in order
82           to instantiate a specific template unit once for each device that
83           appears and matches specific properties.
84
85       SYSTEMD_ALIAS=
86           Adds an additional alias name to the device unit. This must be an
87           absolute path that is automatically transformed into a unit name.
88           (See above.)
89
90       SYSTEMD_READY=
91           If set to 0, systemd will consider this device unplugged even if it
92           shows up in the udev tree. If this property is unset or set to 1,
93           the device will be considered plugged if it is visible in the udev
94           tree.
95
96           This option is useful for devices that initially show up in an
97           uninitialized state in the tree, and for which a "changed" event is
98           generated the moment they are fully set up. Note that
99           SYSTEMD_WANTS= (see above) is not acted on as long as
100           SYSTEMD_READY=0 is set for a device.
101
102       ID_MODEL_FROM_DATABASE=, ID_MODEL=
103           If set, this property is used as description string for the device
104           unit.
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OPTIONS

107       Device unit files may include [Unit] and [Install] sections, which are
108       described in systemd.unit(5). No options specific to this file type are
109       supported.
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SEE ALSO

112       systemd(1), systemctl(1), systemd.unit(5), udev(7),
113       systemd.directives(7)
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117systemd 253                                                  SYSTEMD.DEVICE(5)
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