lm_sensors

Resources

lm_sensors is a set of hardware monitoring user space utilities. They are helpful for tracking temperature, fan, and voltage data. This article deals with the sensors aspect to lm_sensors, but the package also controls software to control fan speed: see the page for fan speed control for details.

Installation

Before lm_sensors will work as intended, the currently running Linux kernel must have the proper modules available to or built-in to the binary in order to give lm_sensors the sensor-related data needed for correct operation. There is a chance these modules have been previously built as modules or are currently included the Kernel's binary (built-in). It is also possible the Kernel is lacking the modules or features. If something is missing then the user will have to take the actions necessary to correct the absence.

In any case a simple hardware detection should be performed using the sensors-detect tool to scan the hardware on the motherboard. Once the hardware has been determined the program will display the output on what is or is not included in the kernel configuration. This step will be performed after installation during the configuration section below.

Another option is to check the Supported Device List on archive.org. Finally, sensors-detect detects the supported drivers if all drivers in kernel section Hardware Monitoring support are enabled.

Kernel

I2C support is needed along with the following kernel options:

KERNEL Enable I2C_CHARDEV and hardware Monitoring support in the kernel

Device Drivers  --->
    -*- I2C support  --->
        <*>   I2C device interface
    <*> Hardware Monitoring support  --->

        Select a driver, e.g.:
        [*] Intel Core/Core2/Atom temperature sensor (coretemp)

USE flags

Portage knows the global USE flag lm-sensors for enabling support for lm-sensors in other packages.

Local USE flags include:

USE flags for sys-apps/lm-sensors Hardware Monitoring user-space utilities

`contrib`	Installs user contributed configuration files so you don't need to find settings on your own for your system if somebody else has already created such a configuration for sensors/mainboards you are using.
`selinux`	!!internal use only!! Security Enhanced Linux support, this must be set by the selinux profile or breakage will occur
`sensord`	Enable sensord - a daemon that can be used to periodically log sensor readings from hardware health-monitoring chips
`static-libs`	Build static versions of dynamic libraries as well

Data provided by the Gentoo Package Database · Last update: 2024-10-17 12:48 More information about USE flags

Emerge

In case any of the packages having the lm-sensors USE flag is installed, set the flag per package in /etc/portage/package.use or globally in /etc/portage/make.conf and update @world so that sys-apps/lm-sensors will be pulled in as dependency:

root #emerge --ask --changed-use --deep @world

Otherwise install it directly:

root #emerge --ask sys-apps/lm-sensors

Configuration

If all drivers were built into the kernel, skip to the next section and proceed with testing. Otherwise configure the modules as needed.

Modules

Warning
Be aware using sensors-detect to probe the hardware in the system may result in a frozen system. Take some special caution by reading the official documentation before running lm_sensors on IBM Thinkpads.

The sensors-detect (/usr/sbin/sensors-detect) tool can be used to find available sensors and associated kernel modules:

root #sensors-detect

Follow the instructions, it will probe which sensors are available and load the relevant kernel modules. The final question will allow you to write a config file in /etc/modules-load.d that contains the kernel modules that need to be loaded. This will only work if the modules-load runscript is started, add it to the default runlevel if necessary.

If you use /etc/conf.d/modules to declare which kernel modules to load simply add the necessary kernel modules as shown by sensors-detect to it.

Services

OpenRC

Start the sensors daemon now:

root #rc-service lm_sensors start

To start lm_sensors on system boot add it the default runlevel:

root #rc-update add lm_sensors default

systemd

Start the sensors daemons now:

root #systemctl start lm_sensors

Enable the sensors daemon for future boots:

root #systemctl enable lm_sensors

Usage

Invocation

user $sensors --help

Usage: sensors [OPTION]... [CHIP]...
  -c, --config-file     Specify a config file
  -h, --help            Display this help text
  -s, --set             Execute `set' statements (root only)
  -f, --fahrenheit      Show temperatures in degrees fahrenheit
  -A, --no-adapter      Do not show adapter for each chip
      --bus-list        Generate bus statements for sensors.conf
  -u                    Raw output
  -v, --version         Display the program version

Use `-' after `-c' to read the config file from stdin.
If no chips are specified, all chip info will be printed.
Example chip names:
	lm78-i2c-0-2d	*-i2c-0-2d
	lm78-i2c-0-*	*-i2c-0-*
	lm78-i2c-*-2d	*-i2c-*-2d
	lm78-i2c-*-*	*-i2c-*-*
	lm78-isa-0290	*-isa-0290
	lm78-isa-*	*-isa-*
	lm78-*

Testing

Now test if everything works:

user $sensors

coretemp-isa-0000
Adapter: ISA adapter
Core 0:       +48.0°C  (high = +100.0°C, crit = +100.0°C)
Core 1:       +48.0°C  (high = +100.0°C, crit = +100.0°C)

Troubleshooting

See the lm_sensors FAQ.