Linux advanced cases that need to keep in mind

 One of the most in-depth areas of linux is kernerl,check how to go through kernel messages

journalctl -k Show kernel message log from the current boot

           -u            Show logs from the specified unit

service name to see log messages for any service, as in this example:

# journalctl -u NetworkManager.service

# journalctl -u httpd.service

very good examples in digital ocean community    

   

https://www.digitalocean.com/community/tutorials/how-to-use-journalctl-to-view-and-manipulate-systemd-logs

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another in depth-area of linux is security tools

A Linux Basic Security tool is rootkit hunter

Rkhunter (Rootkit Hunter) is an open-source Unix/Linux based scanner tool for Linux systems released under GPL that scans backdoors, rootkits, and local exploits on your systems.

https://www.vultr.com/docs/how-to-install-rkhunter-on-ubuntu

https://www.tecmint.com/install-rootkit-hunter-scan-for-rootkits-backdoors-in-linux/