systemd.device — systemd device configuration files
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 udev Database
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:
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.
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.)
If set, this property is used as description string for the device unit.
systemd(1), systemctl(8), systemd.unit(5), udev(7)