systemd.device — Device unit configuration
device.device
A unit configuration file whose name ends in
".device" encodes information about
a device unit as exposed in the
sysfs/udev(7)
device tree.
This unit type has no specific options. See
systemd.unit(5)
for the common options of all unit configuration
files. The common configuration items are configured
in the generic "[Unit]" and
"[Install]" sections. A separate
"[Device]" section does not exist,
since no device-specific options may be
configured.
systemd will automatically create dynamic device units for all kernel devices that are marked with the "systemd" udev tag (by default all block and network devices, and a few others). This may be used to define dependencies between devices and other units.
Device units are named after the
/sys and
/dev paths they control. Example:
the device /dev/sda5 is exposed
in systemd as dev-sda5.device. For
details about the escaping logic used to convert a
file system path to a unit name see
systemd.unit(5).
The settings of device units may either be configured via unit files, or directly from the udev database (which is recommended). The following udev properties are understood by systemd:
SYSTEMD_WANTS=¶Adds dependencies of
type Wants from
this unit to all listed units. This
may be used to activate arbitrary
units, when a specific device becomes
available. Note that this and the
other tags are not taken into account
unless the device is tagged with the
"systemd" string in
the udev database, because otherwise
the device is not exposed as systemd
unit.
SYSTEMD_ALIAS=¶Adds an additional alias name to the device unit. This must be an absolute path that is automatically transformed into a unit name. (See above.)
SYSTEMD_READY=¶If set to 0, systemd will consider this device unplugged even if it shows up in the udev tree. If this property is unset or set to 1, the device will be considered plugged the moment it shows up in the udev tree. This property has no influence on the behavior when a device disappears from the udev tree. This option is useful to support devices that initially show up in an uninitialized state in the tree, and for which a changed event is generated the moment they are fully set up.
ID_MODEL_FROM_DATABASE=, ID_MODEL=¶If set, this property is used as description string for the device unit.