How to better monitor your Ubuntu Linux PC’s temperature and voltage

As many Linux distributions do not ship with the necessary software installed, you'll need to add it manually. Open your desktop menu and select the terminal application.

From the terminal window, issue the following command on a Ubuntu-based distribution:

At the terminal window, issue the command:

After running the sensors-detect command, you'll be asked a number of questions, which include:

• Some south bridges, CPUs or memory controllers contain embedded sensors. Do you want to scan for them? This is totally safe. (YES/no):
• Some Super I/O chips contain embedded sensors. We have to write to standard I/O ports to probe them. This is usually safe. Do you want to scan for Super I/O sensors? (YES/no):
• Some systems (mainly servers) implement IPMI, a set of common interfaces through which system health data may be retrieved, amongst other things. We first try to get the information from SMBIOS. If we don't find it there, we have to read from arbitrary I/O ports to probe for such interfaces. This is normally safe. Do you want to scan for IPMI interfaces? (YES/no): 
• Some hardware monitoring chips are accessible through the ISA I/O ports. We have to write to arbitrary I/O ports to probe them. This is usually safe though. Yes, you do have ISA I/O ports even if you do not have any ISA slots! Do you want to scan the ISA I/O ports? (yes/NO):
• Do you want to probe the I2C/SMBus adapters now? (YES/no): 

Also: How to install Linux on an old laptop

Answer Yes to all questions. When all questions are answered, it will ask if you want it to present a summary. Press Enter on your keyboard to display the results. Once the results are displayed, sensors-detect will then ask if you want it to automatically add the necessary items to /etc/modules. For mine, it lists coretemp as a module that I should add. Type Yes and those modules will be added. Do note, if sensors-detect lists a large number of modules, you should do a bit of research before allowing the tool to add them all. You might wind up adding modules that are already built into your installed kernel.

If sensors-detect added modules to /etc/module, you can go ahead and reboot so those modules will take effect.