1.\" 2.\" Copyright (c) 2002 M. Warner Losh <imp@FreeBSD.org> 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 13.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 14.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 17.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23.\" SUCH DAMAGE. 24.\" 25.Dd October 19, 2021 26.Dt DEVD 8 27.Os 28.Sh NAME 29.Nm devd 30.Nd "device state change daemon" 31.Sh SYNOPSIS 32.Nm 33.Op Fl dnq 34.Op Fl f Ar file 35.Op Fl l Ar num 36.Sh DESCRIPTION 37The 38.Nm 39daemon provides a way to have userland programs run when certain 40kernel events happen. 41.Pp 42The following options are accepted. 43.Bl -tag -width ".Fl f Ar file" 44.It Fl d 45Run in the foreground instead of becoming a daemon and log additional information for debugging. 46.It Fl f Ar file 47Use configuration file 48.Ar file 49instead of the default 50.Pa /etc/devd.conf . 51If option 52.Fl f 53is specified more than once, the last file specified is used. 54.It Fl l Ar num 55Limit concurrent socket connections to 56.Ar num . 57The default connection limit is 10. 58.It Fl n 59Do not process all pending events before becoming a daemon. 60Instead, call daemon right away. 61.It Fl q 62Quiet mode. 63Only log messages at priority LOG_WARNING or above. 64.El 65.Sh IMPLEMENTATION NOTES 66The 67.Nm 68utility 69is a system daemon that runs in the background all the time. 70Whenever a device is added to or removed from the device tree, 71.Nm 72will execute actions specified in 73.Xr devd.conf 5 . 74For example, 75.Nm 76might execute 77.Xr dhclient 8 78when an Ethernet adapter is added to the system, and kill the 79.Xr dhclient 8 80instance when the same adapter is removed. 81Another example would be for 82.Nm 83to use a table to locate and load via 84.Xr kldload 8 85the proper driver for an unrecognized device that is added to the system. 86.Pp 87The 88.Nm 89utility 90hooks into the 91.Xr devctl 4 92device driver. 93This device driver has hooks into the device configuration system. 94When nodes are added or deleted from the tree, this device will 95deliver information about the event to 96.Nm . 97Once 98.Nm 99has parsed the message, it will search its action list for that kind 100of event and perform the action with the highest matching value. 101For most mundane uses, the default handlers are adequate. 102However, for more advanced users, the power is present to tweak every 103aspect of what happens. 104.Pp 105The 106.Nm 107utility 108reads 109.Pa /etc/devd.conf 110or the alternate configuration file specified with a 111.Fl f 112option and uses that file to drive the rest of the process. 113While the format of this file is described in 114.Xr devd.conf 5 , 115some basics are covered here. 116.Pp 117In the 118.Ic options 119section, one can define multiple directories to search 120for config files. 121The default config file specifies 122.Pa /etc/devd 123and 124.Pa /usr/local/etc/devd 125as directories to search. 126All files in these directories whose names match the pattern 127.Pa *.conf 128are parsed. 129These files are intended to be installed by third party vendors that 130wish to hook into the 131.Nm 132system without modifying the user's other 133config files. 134.Pp 135Since 136.Xr devctl 4 137allows only one active reader, 138.Nm 139multiplexes it, forwarding all events to any number of connected clients. 140Clients connect by opening the SOCK_SEQPACKET 141.Ux 142domain socket at 143.Pa /var/run/devd.seqpacket.pipe . 144.Sh FILES 145.Bl -tag -width ".Pa /var/run/devd.seqpacket.pipe" -compact 146.It Pa /etc/devd.conf 147The default 148.Nm 149configuration file. 150.It Pa /var/run/devd.seqpacket.pipe 151The socket used by 152.Nm 153to communicate with its clients. 154.It Pa /var/run/devd.pipe 155A deprecated socket retained for use with old clients. 156.El 157.Sh SEE ALSO 158.Xr devctl 4 , 159.Xr devd.conf 5 160.Sh HISTORY 161The 162.Nm 163utility first appeared in 164.Fx 5.0 . 165.Sh AUTHORS 166.An M. Warner Losh 167