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.\" $FreeBSD$ 26.\" 27.Dd October 19, 2021 28.Dt DEVD 8 29.Os 30.Sh NAME 31.Nm devd 32.Nd "device state change daemon" 33.Sh SYNOPSIS 34.Nm 35.Op Fl dnq 36.Op Fl f Ar file 37.Op Fl l Ar num 38.Sh DESCRIPTION 39The 40.Nm 41daemon provides a way to have userland programs run when certain 42kernel events happen. 43.Pp 44The following options are accepted. 45.Bl -tag -width ".Fl f Ar file" 46.It Fl d 47Run in the foreground instead of becoming a daemon and log additional information for debugging. 48.It Fl f Ar file 49Use configuration file 50.Ar file 51instead of the default 52.Pa /etc/devd.conf . 53If option 54.Fl f 55is specified more than once, the last file specified is used. 56.It Fl l Ar num 57Limit concurrent socket connections to 58.Ar num . 59The default connection limit is 10. 60.It Fl n 61Do not process all pending events before becoming a daemon. 62Instead, call daemon right away. 63.It Fl q 64Quiet mode. 65Only log messages at priority LOG_WARNING or above. 66.El 67.Sh IMPLEMENTATION NOTES 68The 69.Nm 70utility 71is a system daemon that runs in the background all the time. 72Whenever a device is added to or removed from the device tree, 73.Nm 74will execute actions specified in 75.Xr devd.conf 5 . 76For example, 77.Nm 78might execute 79.Xr dhclient 8 80when an Ethernet adapter is added to the system, and kill the 81.Xr dhclient 8 82instance when the same adapter is removed. 83Another example would be for 84.Nm 85to use a table to locate and load via 86.Xr kldload 8 87the proper driver for an unrecognized device that is added to the system. 88.Pp 89The 90.Nm 91utility 92hooks into the 93.Xr devctl 4 94device driver. 95This device driver has hooks into the device configuration system. 96When nodes are added or deleted from the tree, this device will 97deliver information about the event to 98.Nm . 99Once 100.Nm 101has parsed the message, it will search its action list for that kind 102of event and perform the action with the highest matching value. 103For most mundane uses, the default handlers are adequate. 104However, for more advanced users, the power is present to tweak every 105aspect of what happens. 106.Pp 107The 108.Nm 109utility 110reads 111.Pa /etc/devd.conf 112or the alternate configuration file specified with a 113.Fl f 114option and uses that file to drive the rest of the process. 115While the format of this file is described in 116.Xr devd.conf 5 , 117some basics are covered here. 118.Pp 119In the 120.Ic options 121section, one can define multiple directories to search 122for config files. 123The default config file specifies 124.Pa /etc/devd 125and 126.Pa /usr/local/etc/devd 127as directories to search. 128All files in these directories whose names match the pattern 129.Pa *.conf 130are parsed. 131These files are intended to be installed by third party vendors that 132wish to hook into the 133.Nm 134system without modifying the user's other 135config files. 136.Pp 137Since 138.Xr devctl 4 139allows only one active reader, 140.Nm 141multiplexes it, forwarding all events to any number of connected clients. 142Clients connect by opening the SOCK_SEQPACKET 143.Ux 144domain socket at 145.Pa /var/run/devd.seqpacket.pipe . 146.Sh FILES 147.Bl -tag -width ".Pa /var/run/devd.seqpacket.pipe" -compact 148.It Pa /etc/devd.conf 149The default 150.Nm 151configuration file. 152.It Pa /var/run/devd.seqpacket.pipe 153The socket used by 154.Nm 155to communicate with its clients. 156.It Pa /var/run/devd.pipe 157A deprecated socket retained for use with old clients. 158.El 159.Sh SEE ALSO 160.Xr devctl 4 , 161.Xr devd.conf 5 162.Sh HISTORY 163The 164.Nm 165utility first appeared in 166.Fx 5.0 . 167.Sh AUTHORS 168.An M. Warner Losh 169