Ubuntu really useful commands

To list all local groups which have users assigned to them, use this command:

cut -d: -f1 /etc/group | sort

https://stackoverflow.com/questions/14059916/is-there-a-command-to-list-all-unix-group-names

nogroup is the group analog to the nobody user. It is used for unprivileged processes so that even if something goes wrong the process does not have the permissions to cause any serious damage to an important user or group.

https://unix.stackexchange.com/questions/22520/what-is-nogroup-groups-purpose

yes > /dev/null &

The yes command simply repeatedly writes a string to stdout, the character y by default. Redirecting (>) it to /dev/null simply causes for the stream data to be forgotten. In other words this has no lasting effect on the persistent state of your computer, it is not a harmful command through this lens.

Since the yes command writes a string to stdout without any constraint on the output speed, this will cause for the CPU to reach maximal utilization on one core. This is the cause of the processor temperature increase and associated fan speed increase.

In a modern machine, particularly a well designed one like an Apple laptop, the hardware will protect its self from overheating damage. First by increasing fan speed, then by decreasing processor clock speed, and ultimately by halting the processor. Without intentionally circumventing these features, your hardware did not overheat. The machine is fine.

You mentioned a temperature of 72 °C specifically. This is not a very high temperature for a CPU die. A modest mobile cpu, the i5-7260U, specifies a maximum permissible temperature of 100 °C. You can see the specification as T_Junction in the package specifications section of this page: http://ark.intel.com/products/97539/Intel-Core-i5-7260U-Processor-4M-Cache-up-to-3_40-GHz

https://apple.stackexchange.com/questions/295250/can-running-yes-dev-null-harm-a-mac



killall yes

top (task manager)