devd(8)

NAME

devd - device state change daemon

SYNOPSIS

devd [-Dd] [-f file] [-n]

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 dae

mon.

-f file Use configuration file file instead of the de

fault

/etc/devd.conf. If option -f is specified more

than once,
the last file specified is used.

-n Do not process all pending events before becom

ing a daemon.

Instead, call daemon right away.

IMPLEMENTATION NOTES

The devd utility is a system daemon that runs in the back

ground all the
time. Whenever a device is added to or removed from the de

vice 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
driver has hooks into the device configuration system. When

nodes are
added or deleted from the tree, this device will deliver in

formation
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 de

fault 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 or the alternate con

figuration file
specified with a -f option and uses that file to drive the

rest of the
process. While the format of this file is described in de

vd.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 con

fig files.

All messages that devd receives are forwarded to the UNIX

domain socket
at /var/run/devd.pipe.

FILES

/etc/devd.conf The default devd configuration file.
/var/run/devd.pipe The socket used by devd to communi

cate with its

clients.

SEE ALSO

devctl(4), devd.conf(5)

AUTHORS

M. Warner Losh

BSD November 24, 2005

BSD