The lm-sensors package is the standard software used to monitor things like CPU temperature on Linux. All major distributions include this package. Basic configuration, using the sensors-detect utility, is straightforward. For many systems, running sensors-detect and accepting the defaults is enough to get full functionality.
The basic configuration for lm-sensors will provde temperatures for the CPU and ASUS Prime B250M-C motherboard, but not fan speeds.
To get fan speeds and other hardware information you need to load the kernel for the Nuvotron (formerly Winbond) nct6775. During configuration with other recent ASUS motherboards, sensors-detect recommends loading the coretemp and nct6775 driver, but no mention of nct6775 is made during configuration on the Prime B250M-C.
To load both coretemp and nct6775, first check to make sure both will install:
sudo modprobe coretemp
sudo modprobe nct6775
Next, edit /etc/modules and add the following lines:
coretemp
nct6775
Finally, reboot and when the system comes back up re-run sensors-detect to re-configure, accepting the defaults. Output should be something like this (Note two things: (1) Speed of the CPU fan is reported as fan1, not "cpu_fan"); (2) the example system also has a discrete AMD GPU installed that did not require any special configuration):
$ sudo sensors
asus-isa-0000
Adapter: ISA adapter
cpu_fan: 0 RPM
coretemp-isa-0000
Adapter: ISA adapter
Package id 0: +35.0°C (high = +84.0°C, crit = +100.0°C)
Core 0: +33.0°C (high = +84.0°C, crit = +100.0°C)
Core 1: +31.0°C (high = +84.0°C, crit = +100.0°C)
Core 2: +31.0°C (high = +84.0°C, crit = +100.0°C)
Core 3: +28.0°C (high = +84.0°C, crit = +100.0°C)
acpitz-virtual-0
Adapter: Virtual device
temp1: +27.8°C (crit = +119.0°C)
temp2: +29.8°C (crit = +119.0°C)
nct6793-isa-0290
Adapter: ISA adapter
in0: +0.42 V (min = +0.00 V, max = +1.74 V)
in1: +1.02 V (min = +0.00 V, max = +0.00 V) ALARM
in2: +3.36 V (min = +0.00 V, max = +0.00 V) ALARM
in3: +3.33 V (min = +0.00 V, max = +0.00 V) ALARM
in4: +1.00 V (min = +0.00 V, max = +0.00 V) ALARM
in5: +0.14 V (min = +0.00 V, max = +0.00 V) ALARM
in6: +0.95 V (min = +0.00 V, max = +0.00 V) ALARM
in7: +3.36 V (min = +0.00 V, max = +0.00 V) ALARM
in8: +3.15 V (min = +0.00 V, max = +0.00 V) ALARM
in9: +1.00 V (min = +0.00 V, max = +0.00 V) ALARM
in10: +0.95 V (min = +0.00 V, max = +0.00 V) ALARM
in11: +0.95 V (min = +0.00 V, max = +0.00 V) ALARM
in12: +1.00 V (min = +0.00 V, max = +0.00 V) ALARM
in13: +1.02 V (min = +0.00 V, max = +0.00 V) ALARM
in14: +0.45 V (min = +0.00 V, max = +0.00 V) ALARM
fan1: 906 RPM (min = 0 RPM)
fan2: 669 RPM (min = 0 RPM)
fan3: 946 RPM (min = 0 RPM)
fan6: 0 RPM
SYSTIN: +28.0°C (high = +98.0°C, hyst = +95.0°C) sensor = thermistor
CPUTIN: +33.5°C (high = +80.0°C, hyst = +75.0°C) sensor = thermistor
AUXTIN0: +28.5°C sensor = thermistor
AUXTIN1: +28.0°C sensor = thermistor
AUXTIN2: +28.0°C sensor = thermistor
AUXTIN3: +91.0°C sensor = thermistor
PECI Agent 0: +34.0°C (high = +98.0°C, hyst = +95.0°C)
(crit = +100.0°C)
PECI Agent 0 Calibration: +33.0°C
PCH_CHIP_CPU_MAX_TEMP: +0.0°C
PCH_CHIP_TEMP: +0.0°C
intrusion0: OK
intrusion1: ALARM
beep_enable: disabled
amdgpu-pci-0100
Adapter: PCI adapter
fan1: 2675 RPM
temp1: +38.0°C (crit = +0.0°C, hyst = +0.0°C)