Health Monitoring with lm_sensors

A few years ago, a friend of mine had
problems with his computer. It became unreliable; he would get odd
errors, or the system would hang. He re-installed the operating
system and his key applications, but the problems persisted. This
cost him time, and his time is valuable.The problem turned out to be simple: the cooling fan on his
CPU's heat sink was dead. The overheating CPU, in turn, caused
random problems. He wound up replacing the CPU as well as the heat
sink, because the CPU had been damaged.He could have avoided all of this if he had been running some
sort of computer health monitoring system, such as
lm_sensors.lm_sensors is a set of Linux kernel modules for monitoring
the vital signs of a computer: the voltages from the power supply,
the temperature of the system and the CPU and fan speeds.
lm_sensors includes a command-line utility for checking the current
readings. A variety of graphical tools also are available for
putting a pretty face on lm_sensors.Installing lm_sensorsBefore you attempt to install the lm_sensors kernel module,
you should have the I2C driver modules installed. I2C, which stands
for Inter-IC bus, is a simple serial data system for connecting
chips so they can talk to one another. Most motherboards with
health monitoring features use an I2C bus to access those
features.Make sure the I2C drivers are installed on your system. (If
you build your own kernel, the I2C options are located under
Character Devices.)Install the packages that provide lm_sensors, or build it
from source code and install. Then enter
sensors-detect, a script that figures out how to
install lm_sensors on your system. It will try various I2C modules
and then try various lm_sensors modules, until it finds a
combination that works on your system. When it is done, it provides
instructions for how to set up configuration files in /etc, which
load the correct modules when your system boots.Once the modules for lm_sensors are installed and working,
you can run the sensors command
from a shell and receive some useful output. But you probably
aren't done yet.Customizing lm_sensorsYour next step is to edit the /etc/sensors.conf file. This
file sets some custom parameters that make lm_sensors work with
your computer system. For example, you can add a label that changes
Temp1 to CPU Temp; you can disable Temp3 completely if you don't
have a sensor and it is reporting nonsense; and you can customize
the math functions used to calculate the displayed values.Ideally, before you edit /etc/sensors.conf, you should reboot
your computer and enter the BIOS setup screens. (For most
computers, you hit the Del key or the F1 key during bootup to enter
the BIOS. Check the owner's manual for your system, or watch the
screen during bootup for a message like Hit <Del> to
enter Setup.) The BIOS setup should have a sub-menu
showing the same numbers you would like lm_sensors to report. Make
a note of the readings you are seeing. For example, if the CPU
temperature is about 60 degrees Celsius, write that down.Now, booted back into Linux, run the sensors command. If the
numbers are all there and look correct, you are done. If not, you
need to customize /etc/sensors.conf.
Sample sensors Output
Take a look at the top of the output of the sensors command;
it shows you with which chip lm_sensors is communicating. Find that
chip in /etc/sensors.conf and look at the settings you can
customize. /etc/sensors.conf is liberally commented, making it
easier to figure out what you need to do. You also can read the man
page, man sensors.conf.Once you have customized /etc/sensors.conf, you must run the
command sensors -s to put your changes into
effect. Then run the sensors command once again to inspect the
values it reports.Additionally, you should make sure sensors
-s runs each time your system boots.SensordYou have the option to install sensord, the lm_sensors
monitoring dæmon. You can configure this to log either to
standard log files or to a round-robin database (a constant-size
database set up to hold, for example, a week's worth of readings;
new readings overwrite the oldest). By editing /etc/syslog.conf,
you can arrange to receive e-mail when sensor readings go out of
bounds./proclm_sensors creates files under /proc with sensor values in
them. You can create a custom monitoring system by writing scripts
that check the values from these files or parse the results of the
sensors command.The source distribution for lm_sensors includes a simple
Bourne shell dæmon, healthd.sh, that sends e-mail to the root
account if any sensors indicate an alarm state.GUI Clients

A bunch of programs are available that check lm_sensors
values or display them in some cool-looking fashion, including
applets for KDE and GNOME and several window managers. The
resources section has some links to get you started.I've been running the elaborate GKrellM, a GTK applet
designed to make an impressive panel of monitors. The screenshot to
the right shows it running on my system, with not only lm_sensors
data but also with S.M.A.R.T. hard disk temperature data and the
BubbleFishyMon plugin. (BubbleFishyMon represents memory load as
the water level, CPU activity as bubbles and network packets as
fish swimming back and forth. The rubber duck is just for
fun.)ConclusionIt takes a bit of work to get lm_sensors working on your
system, but it's well worth it. You might catch a hardware
malfunction early, before it becomes serious. Even if you don't
have any problems, it's reassuring to be able to check up on the
health of your system quickly.Resourceslm_sensors Home
Pagelm_sensors
FAQ Filelm_sensors
Related Projects at Freshmeat.netGKrellM, the System
Monitor from the Forbidden PlanetBubbleFishyMon, a
Plugin for GKrellMhddtemp,
a Plugin that Monitors Hard Disk Temperature Using
S.M.A.R.T.xsensors,
a Simple lm_sensors Display that Uses GTK widgetsSteve Hastings first used
UNIX on actual paper teletypes. He enjoys bicycling, music, petting
his cat and making his Linux computers do new things.

email: srhastings@langri.com