5a882d775d
'd': now means don't do daemon(). 'D': Debug 'n': Don't wait to process all pending events before calling daemon. In the past, devd would call daemon immediately. However, this causes a race. If anything in the boot process depends on configuring the devices configured by devd, maybe they would be configured in time, maybe not. Now we don't call daemon until all pending events are processed, unless -n is specified. # -n is actually the default for a while due to the select(2) bug in devctl # that I just fixed to give people a chance to upgrade.
117 lines
3.4 KiB
Groff
117 lines
3.4 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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Don't process all pending events before becoming a daemon.
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Instaed, 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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.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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