[1] https://www.howtogeek.com/412055/37-important-linux-commands-you-should-know/
[2] https://fossbytes.com/a-z-list-linux-command-line-reference/
[3] https://www.tecmint.com/linux-commands-cheat-sheet/
[4] https://www-uxsup.csx.cam.ac.uk/pub/doc/suse/suse9.0/userguide-9.0/ch24s04.html
[5] https://searchdatacenter.techtarget.com/tutorial/77-Linux-commands-and-utilities-youll-actually-use