free

use to get a detailed report on the system's memory usage.

scp

securely copy files or directories over ssh

find

locates files using user-defined criteria

ncdu

provides a useful and convenient way to view disk usage

ip

used to show or manipulate routing, devices, and tunnels

ls

list the contents of a directory

df

Displays the amount of disk space used

du

display a list of all the files along with their respective sizes

uptime

displays the system uptime as well as the load average.

diff

used to display differences in files by comparing them line by line.

top

shows a real-time view of running processes in Linux.

dstat

allows you to view all of your system resources instantly. All-in-one vmstat, iostat, netstat, and ifstat utility.

Note :- sudo apt install dstat

Iftop

is a network traffic viewer

nethogs

is a network traffic analyzer.