X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=man%2Fsystemd.device.xml;h=1bbd32248fce34226dd9359068ff2190d0d7d10b;hp=3f6d012c11bf72fe54db45343f348e1bdb121bbe;hb=b408e2a8be6b87fd1796c45a767d00bbb00d7148;hpb=e670b166a08b7c1031a9e7d7675fa9a29c3e19c9 diff --git a/man/systemd.device.xml b/man/systemd.device.xml index 3f6d012c1..1bbd32248 100644 --- a/man/systemd.device.xml +++ b/man/systemd.device.xml @@ -55,7 +55,7 @@ Description A unit configuration file whose name ends in - .device encodes information about + .device encodes information about a device unit as exposed in the sysfs/udev7 device tree. @@ -70,17 +70,20 @@ 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. + 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 + udev7 + for details. Device units are named after the /sys and /dev paths they control. Example: - the device /dev/sda5 is exposed + 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 @@ -93,24 +96,41 @@ The settings of device units may either be configured via unit files, or directly from the udev - database (which is recommended). The following udev + database (which is recommended). The following udev device properties are understood by systemd: SYSTEMD_WANTS= + SYSTEMD_USER_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 + 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 + available. + + Note that this and the other tags are not taken into account unless the device is tagged with the - "systemd" string in + systemd string in the udev database, because otherwise - the device is not exposed as systemd - unit. + 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 dependencies. + @@ -124,21 +144,27 @@ SYSTEMD_READY= - If set to 0 systemd + 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 + to 1, the device will be considered + plugged if it 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 + 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. + 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.