Check and Monitor CPU Temperature

The kernel exposes each ACPI thermal zone as a directory named /sys/class/thermal/thermal_zoneN. Reading these files requires neither the sensors package nor special privileges.

> grep . /sys/class/thermal/thermal_zone*/{type,temp}

/sys/class/thermal/thermal_zone0/type:acpitz
/sys/class/thermal/thermal_zone1/type:acpitz
/sys/class/thermal/thermal_zone0/temp:40900
/sys/class/thermal/thermal_zone1/temp:52900

The grep . command prints the name of each file in front of its content, so that every value stays assigned to its zone. The temperature is given in millidegrees Celsius: 40900 means 40.9°C. The type acpitz identifies an ACPI thermal zone.

If /sys/class/thermal contains no thermal_zoneN directory, the system has no ACPI thermal zone. Use the sensors command instead.

Each zone can define trip points. To list the first trip point of the first zone, run:

> grep . /sys/class/thermal/thermal_zone0/trip_point_0_{type,temp}

/sys/class/thermal/thermal_zone0/trip_point_0_type:critical
/sys/class/thermal/thermal_zone0/trip_point_0_temp:100000

A trip point of type critical gives the temperature at which the kernel shuts down the system to protect the hardware. Its value is also in millidegrees Celsius: 100000 means 100°C. When a zone reaches this temperature, the kernel logs the messages critical temperature reached and HARDWARE PROTECTION shutdown (Temperature too high).

You can recognize a reading that comes through ACPI in two ways:

To see the name that the system firmware gave to each zone, read the path file of the zone:

> grep . /sys/class/thermal/thermal_zone*/device/path

/sys/class/thermal/thermal_zone0/device/path:\_TZ_.TZ00
/sys/class/thermal/thermal_zone1/device/path:\_TZ_.TZ01

The kernel reports that a reading comes through ACPI, but not which component the zone measures. The firmware chooses the names.

Sensors that the sensors command lists under another chip name, such as the NVMe drive nvme-pci-0090 in the following section, are provided by their own kernel drivers and do not come through ACPI.

The sensors command lists every temperature sensor that the kernel has registered, not only the ACPI thermal zones. It needs the sensors package, as described in Section 2, “Installing and configuring hardware sensors”, but no special privileges. To obtain a snapshot of the current temperatures, run:

> sensors

Sample output:

nvme-pci-0090 1
Adapter: PCI adapter 2
Composite:    +49.9°C  (low  = -273.1°C, high = +69.8°C)3
                       (crit = +99.8°C)

acpitz-acpi-0 4
Adapter: ACPI interface
temp1:        +40.9°C
temp2:        +52.9°C

The sensors command lists the sensors that the kernel has already registered. It does not depend on sensors-detect, which only searches for additional chips (see Section 2, “Installing and configuring hardware sensors”). The kernel drivers coretemp for Intel processors and k10temp for AMD processors provide the CPU temperature.

Note: Output depends on the type of hardware

The output of the sensors command depends on the type of hardware installed on your machine, as different hardware components have different sensors.

If you suspect that the displayed temperature is too low or too high, you can try the following:

If none of these recommendations solve the issue, the problem might be due to unsupported or faulty hardware. In this case, you need to seek help from your hardware manufacturer.

If the CPU temperature is too high, here are actions you can take: