Ubuntu Guide shows you how to install Psensor to monitor your CPU/NVdia GPUs/Hard Disk temperature in Ubuntu

Psensor is a graphical hardware temperature monitor for Linux.

It can monitor:

the temperature of the motherboard and CPU sensors (using lm-sensors).
the temperature of the NVidia GPUs (using XNVCtrl).
the temperature of the Hard Disk Drives (using hddtemp).
the rotation speed of the fans (using lm-sensors)

  Monitor CPU/NVdia GPUs/Hard Disk temperature in Ubuntu using Psensor