Provided by: systemd_229-4ubuntu21.31_amd64 bug


       systemd.device - Device unit configuration




       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 dynamically create 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. To tag a udev device,
       use "TAG+="systemd"" in the udev rules file, see udev(7) for details.

       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).


       Many unit types automatically acquire dependencies on device units of devices they
       require. For example, .socket unit acquire dependencies on the device units of the network
       interface specified in BindToDevice=. Similar, swap and mount units acquire dependencies
       on the units encapsulating their backing block devices.


       The settings of device units may either be configured via unit files, or directly from the
       udev database (which is recommended). The following udev device properties are understood
       by systemd:

           Adds dependencies of type Wants from the device unit to all listed units. The first
           form is used by the system systemd instance, the second by user systemd instances.
           Those settings may be used to activate arbitrary units when a specific device becomes

           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 a systemd unit (see above).

           Note that systemd will only act on Wants dependencies when a device first becomes
           active. It will not act on them if they are added to devices that are already active.
           Use SYSTEMD_READY= (see below) to influence on which udev event to trigger the

           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 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 if it is visible 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. Note that SYSTEMD_WANTS= (see above) is not acted on as long as
           SYSTEMD_READY=0 is set for a device.

           If set, this property is used as description string for the device unit.


       systemd(1), systemctl(1), systemd.unit(5), udev(7), systemd.directives(7)