Press CTRL + V to enable Visual Mode.
Using the up and down arrow key, highlight the lines you wish to comment out.
Once you have the lines selected, press the SHIFT + I keys to enter insert mode.
Enter your command symbol, for example, # sign, and press the ESC key. Vim will comment out all the highlighted lines.
How to Stress Test Your Raspberry Pi
Now it's time to find out what your Pi is really made of. Open up a terminal window and enter the following to download Stress and cpuburn-a53:
sudo apt-get install stress
gcc -o cpuburn-a53 cpuburn-a53.S
Now to run these tests, we're going to be monitoring the ARM CPU frequency to see whether the Pi automatically throttles the speed (indicates temperature of 80C) and the core temperature. Pay close attention to these, and if the temperature gets too hot, be prepared to pull the power. It's a good idea to run these tests on a fresh image of Raspbian to ensure that any important files don't get corrupted in case you need to pull the power (in case of a system freeze, crash or over-temp).
**If you need to shutdown your system while it's non-responsive, try pressing alt prtscr b before pulling the power, if that doesn't work, then remove the power supply**
To run Stress, use the following terminal command:
while true; do vcgencmd measure_clock arm; vcgencmd measure_temp; sleep 10; done& stress -c 4 -t 900s
Monitor the CPU frequency and temperature for 10mins and only move on to cpuburn-a53 if the test is run for 10mins without throttling or 80C temperatures.