home | help 
DEVD(8) 		     System Manager's Manual			 DEVD(8)

NAME
     devd -- device state change daemon

SYNOPSIS
     devd [-Ddn]

DESCRIPTION
     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.

IMPLEMENTATION NOTES
     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  system,  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 dri-
     ver 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  match-
     ing value.  For most mundane uses, the default handlers are adequate.  How-
     ever,  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 files.

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

SEE ALSO
     devctl(4), devd.conf(5)

AUTHORS
     M. Warner Losh

FreeBSD 5.5			October 17, 2002			 DEVD(8)
home | help