lm-sensors/prog/sensord/sensord.8

.\" Copyright 1999-2002 Merlin Hughes <merlin@merlin.org>
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.TH sensord 8  "October 2007" "lm-sensors 3" "Linux System Administration"
.SH NAME
sensord \- Sensor information logging daemon.
.SH SYNOPSIS
.B sensord [
.I options
.B ] [
.I chips
.B ]

.SH DESCRIPTION
.B Sensord
is a daemon that can be used to periodically log sensor readings from
hardware health-monitoring chips to
.BR syslog (3)
or a round-robin database (RRD)
and to alert when a sensor alarm is signalled; for example, if a
fan fails, a temperature limit is exceeded, etc.

.SH OPTIONS
.IP "-i, --interval time"
Specify the interval between scanning for sensor alarms; the default is to
scan every minute.

The time should be specified as a raw integer (seconds) or with a suffix
`s' for seconds, `m' for minutes or `h' for hours; for example, the
default interval is `60' or `1m'.

Specify an interval of zero to suppress scanning explicitly for alarms.
.IP "-l, --log-interval time"
Specify the interval between logging all sensor readings; the default is
to log all readings every half hour.

The time is specified as before; e.g., `30m'.

Specify an interval of zero to suppress logging of regular sensor
readings.
.IP "-t, --rrd-interval time"
Specify the interval between logging all sensor readings to a round-robin
database; the default is to log all readings every five minutes
.B if
a round-robin database is configured.

The time is specified as before; e.g., `5m'.
.IP "-T, --rrd-no-average"
Specify that the round-robin database should not be averaged.

.IP "-r, --rrd-file file"
Specify a round-robin database into which to log all sensor readings;
e.g., `/var/log/sensord.rrd'. This database will be created if it does
not exist. By default, no round-robin database is used.

See the section
.B ROUND ROBIN DATABASES
below for more details.
.IP "-c, --config-file file"
Specify a
.BR libsensors (3)
configuration file. If no file is specified, the libsensors default
configuration file is used.

.IP "-p, --pid-file file"
Specify what PID file to write; the default is to write the file
`/var/run/sensord.pid'. You should always specify an absolute path
here. The file is removed when the daemon exits.
.IP "-f, --syslog-facility facility"
Specify the
.BR syslog (3)
facility to use when logging sensor readings and alarms; the default is
to use
.IR local4 .

Other possibile facilities include
.IR local0
through
.IR local7 ,
.IR daemon
or
.IR user .
.IP "-g, --rrd-cgi directory"
Prints out a sample
.BR rrdcgi (1)
CGI script that can be used to display graphs of recent sensor information
in a Web page, and exits. You must specify the world-writable, Web-accessible
directory where the graphs should be stored; the CGI script assumes that
this will be accessed under the `/sensord/' directory on the Webserver. See
the section
.B ROUND ROBIN DATABASES
below for more details.
.IP "-a, --load-average"
Include the load average in the RRD database. You should
also specify this flag when you create the CGI script.
.IP "-d, --debug"
Prints a small amount of additional debugging information.
.IP "-h, --help"
Prints a help message and exits.
.IP "-v, --version"
Displays the program version and exits.
.SH CHIPS
To restrict the devices that are scanned by this daemon, you may
optionally specify a list of chip names. By default, all available
chips are scanned.

A typical chip name would be `w83782d-*' (you may want to escape the
`*' for your shell) which would scan any W83782D chips on any bus. See
.BR sensors.conf (5)
for more details. Another option is to simply not load the sensor
modules for chips in which you have no interest.
.SH SIGNALS
Upon receipt of a SIGTERM (see
.BR signal (7)
for details) this daemon should gracefully shut down.

Upon receipt of a SIGHUP, this daemon will rescan the kernel interface
for chips and features, and reload the libsensors configuration file.
.SH LOGGING
All messages from this daemon are logged to
.BR syslog (3)
under the program name `sensord' and facility
.IR local4 ,
or whatever is specified on the command line.

Regular sensor readings are logged at the level
.IR info .
Alarms are logged at the level
.IR alert .
Inconsequential status messages are logged at
the minimum level,
.IR debug ,
when debugging is enabled.

You can use an appropriate `/etc/syslog.conf'
file to direct these messages in a useful manner. See
.BR syslog.conf (5)
for full details, however the following is a sample configuration:
.IP
.nf
# Sample syslog.conf entries
*.info;...;local4.none;local4.warn  /var/log/messages
local4.info                        -/var/log/sensors
local4.alert                        /dev/console
local4.alert                        *
.fi
.PP
The first line ensures that regular sensor readings do not clutter
`/var/log/messages'; we first say `local4.none' to eliminate
informational messages; then `local4.warn' to enable warnings and
above. The second line says to log all regular sensor readings to
`/var/log/sensors'; the leading hyphen `-' means that this file
is not flushed after every message. The final two lines ensure
that alarms are printed to the system console as well as
to all connected users (in addition to `/var/log/messages' and
`/var/log/sensors').
.SH LOG ROTATION
On a typical system with a good sensor chip, expect about 2KB per sensor
reading in the log file. This works out at about 3MB per month. You
should be rotating your syslog files anyway, but just to be sure you'll
want to use something like
.BR logrotate (8)
or equivalent. You might, for example, want an entry in
`/etc/logrotate.d/syslog' containing:
.IP
.nf
# Sample logrotate.d entry
/var/log/sensors {
    postrotate
        /usr/sbin/killall -HUP syslogd
    endscript
}
.fi
.PP
Note, of course, that you want to restart
.BR syslogd (8)
and not
.BR sensord (8)
.
.SH ALARMS
Alarms generally indicate a critical condition; for example, a fan
failure or an unacceptable temperature or voltage. However, some
sensor chips do not support alarms, while others are incorrectly
configured and may signal alarms incorrectly.

Note that some drivers may lack support for alarm reporting
even though the chips they support do have alarms. As of Linux 2.6.23,
many drivers still don't report alarms in a format suitable for
libsensors 3.

.SH BEEPS
If you see `(beep)' beside any sensor reading, that just means that
your system is configured to issue an audio warning from the
motherboard if an alarm is signalled on that sensor.
.SH ROUND ROBIN DATABASES
.BR Sensord (8)
provides support for storing sensor readings in a round-robin
database. This may be a useful alternative to the use of
.BR syslog (3).

Round-robin databases are
constant-size databases that can be used to store, for example,
a week's worth of sensor readings. Subsequent readings stored
in the database will overwrite readings that are over a week
old. This capability is extremely useful because it allows
useful information to be stored in an easily-accessible
manner for a useful length of time, without the burden of
ever-growing log files.

The
.BR rrdtool (1)
utility and its associated library provide the basic framework for
the round-robin database beneath
.BR sensord (8).
In addition, the
.BR rrdcgi (1)
and
.BR rrdgraph (1)
utilities provide support for generating graphs of these data for
display in a Web page.

If you wish to use the default configuration of round-robin
database, which holds one week of sensor readings at five-minute
intervals, then simply start
.BR sensord (8)
and specify where you want the database stored. It will automatically
be created and configured using these default parameters.

If you wish readings to be stored for a longer period, or want multiple
readings to be averaged into each database entry, then you must
manually create and configure the database before starting
.BR sensord (8).
Consult the
.BR rrdcreate (1)
manual for details. Note that the database must match exactly the
names and order of sensors read by
.BR sensord (8).
It is recommended that you create the default database and then use
.BR rrdinfo (1)
to obtain this information, and/or
.BR rrdtune (1)
to change it.

After creating the round-robin database, you must then configure
your Web server to display the sensor information. This assumes that
you have a Web server preconfigured and functioning on your machine.
.BR Sensord (8)
provides a command-line option
.BR --rrd-cgi
to generate a basic CGI script to
display these graphs; you can then customize this script as desired.
Consult the
.BR rrdcgi (1)
manual for details. This CGI script requires a world-writable, Web-accessible
directory into which to write the graphs that it generates.

An example of how to set up Web-accessible graphs of recent sensor readings
follows:
.IP
.nf
sensord --log-interval 0 \\
  --load-average \\
  --rrd-file /var/log/sensord.rrd
.fi
.PP
Here, we start
.BR sensord (8)
and configure it to store readings in a round-robin database; note
that we disable logging of sensor readings to
.BR syslog (3),
and enable logging of the load average.
.IP
.nf
mkdir /var/www/sensord
chown www-data:staff /var/www/sensord
chmod a=rwxs /var/www/sensord
.fi
.PP
Here, we create a world-writable, Web-accessible directory in which
graphs will be stored; we set the ownership and permissions on this
directory appropriately. You will have to determine the location and
ownership that is appropriate for your machine.
.IP
.nf
sensord --load-average \\
  --rrd-file /var/log/sensord.rrd \\
  --rrd-cgi /var/www/sensord \\
  > /usr/lib/cgi-bin/sensord.cgi
chmod a+rx /usr/lib/cgi-bin/sensord.cgi
.fi
.PP
Here, we create
a CGI script that will display sensor readings from the database.
You must specify the location of the round-robin database, the
location of the directory where the images should be stored,
and whether you want the load average displayed. The
.BR --rrd-cgi
command-line parameter causes
.BR sensord (8)
to display a suitable CGI script on
.BR stdout
and then to exit. You will need to write this script to the CGI
bin directory of your Web server,
and edit the script if the image directory you chose is not the
`/sensord/' directory of your Web server.

Finally, you should be able to view your sensor readings from
the URL `http://localhost/cgi-bin/sensord.cgi'.
.SH MODULES
It is expected that all required sensor modules are loaded prior to
this daemon being started. This can either be achieved with a system
specific module loading scheme (e.g., listing the required modules
in the file `/etc/modules' under Debian) or with explicit
.BR modprobe (1)
commands in an init script before loading the daemon.

For example, a `sensord' initialization script might
contain (among others) the following commands:
.IP
.nf
# Sample init.d scriptlet
echo -n "Loading AMD756 module: "
modprobe i2c-amd756 || { echo Fail. ; exit 1 ; }
echo OK.
echo -n "Loading W83781D module: "
modprobe w83781d || { echo Fail. ; exit 1 ; }
echo OK.
echo -n "Starting sensord: "
daemon sensord
...
.fi
.PP
Ignore the platform-specific shell functions; the general idea
should be fairly clear.
.SH ERRORS
Errors encountered by this daemon are logged to
.BR syslogd (8)
after which the daemon will exit.
.SH BUGS
Round-robin database support doesn't cope with
multiple sensor chips having duplicate sensor labels.
.SH FILES
.I /etc/sensors3.conf
.br
.I /etc/sensors.conf
.RS
The system-wide
.BR libsensors (3)
configuration file. See
.BR sensors.conf (5)
for further details.
.RE
.I /etc/syslog.conf
.RS
The system-wide
.BR syslog (3)
/
.BR syslogd (8)
configuration file. See
.BR syslog.conf (5)
for further details.
.RE

.SH SEE ALSO
sensors.conf(5)
.SH AUTHORS
.B Sensord
was written by Merlin Hughes <merlin@merlin.org>. Basics of round-robin
databases were misappropriated from Mark D. Studebaker.