1.\" 2.\" Copyright (c) 2002 M. Warner Losh. 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24.\" SUCH DAMAGE. 25.\" 26.\" $FreeBSD$ 27.\" 28.Dd October 5, 2016 29.Dt DEVD 8 30.Os 31.Sh NAME 32.Nm devd 33.Nd "device state change daemon" 34.Sh SYNOPSIS 35.Nm 36.Op Fl dnq 37.Op Fl f Ar file 38.Op Fl l Ar num 39.Sh DESCRIPTION 40The 41.Nm 42daemon provides a way to have userland programs run when certain 43kernel events happen. 44.Pp 45The following options are accepted. 46.Bl -tag -width ".Fl f Ar file" 47.It Fl d 48Run in the foreground instead of becoming a daemon and log additional information for debugging. 49.It Fl f Ar file 50Use configuration file 51.Ar file 52instead of the default 53.Pa /etc/devd.conf . 54If option 55.Fl f 56is specified more than once, the last file specified is used. 57.It Fl l Ar num 58Limit concurrent socket connections to 59.Ar num . 60The default connection limit is 10. 61.It Fl n 62Do not process all pending events before becoming a daemon. 63Instead, call daemon right away. 64.It Fl q 65Quiet mode. 66Only log messages at priority LOG_WARNING or above. 67.El 68.Sh IMPLEMENTATION NOTES 69The 70.Nm 71utility 72is a system daemon that runs in the background all the time. 73Whenever a device is added to or removed from the device tree, 74.Nm 75will execute actions specified in 76.Xr devd.conf 5 . 77For example, 78.Nm 79might execute 80.Xr dhclient 8 81when an Ethernet adapter is added to the system, and kill the 82.Xr dhclient 8 83instance when the same adapter is removed. 84Another example would be for 85.Nm 86to use a table to locate and load via 87.Xr kldload 8 88the proper driver for an unrecognized device that is added to the system. 89.Pp 90The 91.Nm 92utility 93hooks into the 94.Xr devctl 4 95device driver. 96This device driver has hooks into the device configuration system. 97When nodes are added or deleted from the tree, this device will 98deliver information about the event to 99.Nm . 100Once 101.Nm 102has parsed the message, it will search its action list for that kind 103of event and perform the action with the highest matching value. 104For most mundane uses, the default handlers are adequate. 105However, for more advanced users, the power is present to tweak every 106aspect of what happens. 107.Pp 108The 109.Nm 110utility 111reads 112.Pa /etc/devd.conf 113or the alternate configuration file specified with a 114.Fl f 115option and uses that file to drive the rest of the process. 116While the format of this file is described in 117.Xr devd.conf 5 , 118some basics are covered here. 119In the 120.Ic options 121section, one can define multiple directories to search 122for config files. 123All files in these directories whose names match the pattern 124.Pa *.conf 125are parsed. 126These files are intended to be installed by third party vendors that 127wish to hook into the 128.Nm 129system without modifying the user's other 130config files. 131.Pp 132Since 133.Xr devctl 4 134allows only one active reader, 135.Nm 136multiplexes it, forwarding all events to any number of connected clients. 137Clients connect by opening the SOCK_SEQPACKET 138.Ux 139domain socket at 140.Pa /var/run/devd.seqpacket.pipe . 141.Sh FILES 142.Bl -tag -width ".Pa /var/run/devd.seqpacket.pipe" -compact 143.It Pa /etc/devd.conf 144The default 145.Nm 146configuration file. 147.It Pa /var/run/devd.seqpacket.pipe 148The socket used by 149.Nm 150to communicate with its clients. 151.It Pa /var/run/devd.pipe 152A deprecated socket retained for use with old clients. 153.El 154.Sh SEE ALSO 155.Xr devctl 4 , 156.Xr devd.conf 5 157.Sh HISTORY 158The 159.Nm 160utility first appeared in 161.Fx 5.0 . 162.Sh AUTHORS 163.An M. Warner Losh 164