[PATCH] add comment in wait_for_sysfs to explain the structure better.

[thirdparty/systemd.git] / udevd.8

.TH UDEVD 8 "February 2004" "" "Linux Administrator's Manual"
.SH NAME
udevd, udevdsend \- udev event serializer daemon and udev event sender
.SH SYNOPSIS
.BI udevsend " hotplug-subsystem"
.sp
The environment must provide the following variables:
.TP
.B ACTION
.IR add " or " remove
signifies the connection or disconnection of a device.
.TP
.B DEVPATH
The sysfs devpath of the device without the mountpoint but a leading slash.
.TP
.B SEQNUM
The sequence number of the event provided by the kernel.
If unset, the event bypasses the queue and will be executed immediately.
.SH "DESCRIPTION"
.B udevd
allows the serialization of
.BR hotplug (8)
events. The events generated by the kernel may arrive in random order
in userspace, that makes it neccessary to reorder them.
.br
.B udevd
takes care of the kernel supplied sequence number and arranges the events for
execution in the correct order. Missing sequences delay the execution of the
following events until a timeout is reached.
.br
For each event a
.BR udev (8)
instance is executed in the background. All further events for the same device
are delayed until the execution is finished. This way there will never be more
than one instance running for a single device at the same time.
.br
.B udevd
receives the events from
.B udevsend
which is called by
.BR hotplug (8).
If
.B udevd
isn't already running,
.B udevsend
will start it.
.SH "SEE ALSO"
.BR udev (8),
.BR udevinfo (8),
.BR hotplug (8)
.SH AUTHORS
.B udevd
was developed primarily by Kay Sievers <kay.sievers@vrfy.org>, with much help
from others.