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.TH "SYSTEMD\&.DEVICE" "5" "" "systemd 215" "systemd.device"
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.\" -----------------------------------------------------------------
.\" * Define some portability stuff
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.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.\" http://bugs.debian.org/507673
.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.ie \n(.g .ds Aq \(aq
.el       .ds Aq '
.\" -----------------------------------------------------------------
.\" * set default formatting
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.\" disable hyphenation
.nh
.\" disable justification (adjust text to left margin only)
.ad l
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.\" * MAIN CONTENT STARTS HERE *
.\" -----------------------------------------------------------------
.SH "NAME"
systemd.device \- Device unit configuration
.SH "SYNOPSIS"
.PP
\fIdevice\fR\&.device
.SH "DESCRIPTION"
.PP
A unit configuration file whose name ends in
"\&.device"
encodes information about a device unit as exposed in the sysfs/\fBudev\fR(7)
device tree\&.
.PP
This unit type has no specific options\&. See
\fBsystemd.unit\fR(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\&.
.PP
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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
\fBudev\fR(7)
for details\&.
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.PP
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
\fBsystemd.unit\fR(5)\&.
.SH "THE UDEV DATABASE"
.PP
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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:
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.PP
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\fISYSTEMD_WANTS=\fR, \fISYSTEMD_USER_WANTS=\fR
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.RS 4
Adds dependencies of type
\fIWants\fR
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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\&.
.sp
Note that this and the other tags are not taken into account unless the device is tagged with the
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"systemd"
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string in the udev database, because otherwise the device is not exposed as a systemd unit (see above)\&.
.sp
Note that systemd will only act on
\fIWants\fR
dependencies when a device first becomes active\&. It will not act on them if they are added to devices that are already active\&. Use
\fISYSTEMD_READY=\fR
(see below) to influence on which udev event to trigger the dependencies\&.
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.RE
.PP
\fISYSTEMD_ALIAS=\fR
.RS 4
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\&.)
.RE
.PP
\fISYSTEMD_READY=\fR
.RS 4
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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\&.
.sp
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
\fISYSTEMD_WANTS=\fR
(see above) is not acted on as long as
\fISYSTEMD_READY=0\fR
is set for a device\&.
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.RE
.PP
\fIID_MODEL_FROM_DATABASE=\fR, \fIID_MODEL=\fR
.RS 4
If set, this property is used as description string for the device unit\&.
.RE
.SH "SEE ALSO"
.PP
\fBsystemd\fR(1),
\fBsystemctl\fR(8),
\fBsystemd.unit\fR(5),
\fBudev\fR(7),
\fBsystemd.directives\fR(7)