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DEVD(8)			  BSD System Manager's Manual		       DEVD(8)

     devd -- device state change daemon

     devd [-Ddn]

     The devd daemon provides a	way to have userland programs run when certain
     kernel events happen.

     The following options are accepted.

     -D	     Enable debugging messages.

     -d	     Run in the	foreground instead of becoming a daemon.

     -n	     Do	not process all	pending	events before becoming a daemon.  In-
	     stead, call daemon	right away.

     The devd utility is a system daemon that runs in the background all the
     time.  Whenever a device is added to or removed from the device tree,
     devd will execute actions specified in devd.conf(5).  For example,	devd
     might execute dhclient(8) when an Ethernet	adapter	is added to the	sys-
     tem, and kill the dhclient(8) instance when the same adapter is removed.
     Another example would be for devd to use a	table to locate	and load via
     kldload(8)	the proper driver for an unrecognized device that is added to
     the system.

     The devd utility hooks into the devctl(4) device driver.  This device
     driver has	hooks into the device configuration system.  When nodes	are
     added or deleted from the tree, this device will deliver information
     about the event to	devd.  Once devd has parsed the	message, it will
     search its	action list for	that kind of event and perform the action with
     the highest matching value.  For most mundane uses, the default handlers
     are adequate.  However, for more advanced users, the power	is present to
     tweak every aspect	of what	happens.

     The devd utility reads /etc/devd.conf and uses that file to drive the
     rest of the process.  While the format of this file is described in
     devd.conf(5), some	basics are covered here.  In the options section, one
     can define	multiple directories to	search for config files.  All files in
     these directories whose names match the pattern *.conf are	parsed.	 These
     files are intended	to be installed	by third party vendors that wish to
     hook into the devd	system without modifying the user's other config

     All messages that devd receives are forwarded to the UNIX domain socket
     at	/var/run/devd.pipe.

     devctl(4),	devd.conf(5)

     M.	Warner Losh

BSD			       October 17, 2002				   BSD


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