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122 lines
3.5 KiB
Groff
122 lines
3.5 KiB
Groff
.\"
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.\" Copyright (c) 2002 M. Warner Losh.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd October 17, 2002
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.Dt DEVD 8
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.Os
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.Sh NAME
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.Nm devd
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.Nd "device state change daemon"
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.Sh SYNOPSIS
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.Nm
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.Op Fl Ddn
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.Sh DESCRIPTION
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The
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.Nm
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daemon provides a way to have userland programs run when certain
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kernel events happen.
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.Pp
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The following options are accepted.
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.Bl -tag -width indent
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.It Fl D
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Enable debugging messages.
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.It Fl d
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Run in the foreground instead of becoming a daemon.
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.It Fl n
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Do not process all pending events before becoming a daemon.
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Instead, call daemon right away.
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.El
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.Sh IMPLEMENTATION NOTES
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The
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.Nm
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utility
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is a system daemon that runs in the background all the time.
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Whenever a device is added to or removed from the device tree,
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.Nm
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will execute actions specified in
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.Xr devd.conf 5 .
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For example,
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.Nm
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might execute
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.Xr dhclient 8
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when an Ethernet adapter is added to the system, and kill the
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.Xr dhclient 8
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instance when the same adapter is removed.
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Another example would be for
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.Nm
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to use a table to locate and load via
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.Xr kldload 8
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the proper driver for an unrecognized device that is added to the system.
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.Pp
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The
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.Nm
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utility
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hooks into the
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.Xr devctl 4
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device driver.
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This device driver has hooks into the device configuration system.
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When nodes are added or deleted from the tree, this device will
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deliver information about the event to
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.Nm .
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Once
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.Nm
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has parsed the message, it will search its action list for that kind
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of event and perform the action with the highest matching value.
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For most mundane uses, the default handlers are adequate.
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However, for more advanced users, the power is present to tweak every
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aspect of what happens.
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.Pp
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The
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.Nm
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utility
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reads
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.Pa /etc/devd.conf
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and uses that file to drive the rest of the process.
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While the format of this file is described in
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.Xr devd.conf 5 ,
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some basics are covered here.
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In the
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.Ic options
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section, one can define multiple directories to search
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for config files.
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All files in each of these directories are parsed.
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These files are intended to be installed by third party vendors that
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wish to hook into the
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.Nm
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system without modifying the user's other
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config files.
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.Pp
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All messages that
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.Nm
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receives are forwarded to the unix domain socket at
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.Pa /var/run/devd.pipe .
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.Sh SEE ALSO
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.Xr devctl 4 ,
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.Xr devd.conf 5
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.Sh AUTHORS
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.An M. Warner Losh
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