If you want to leave a command running if you are disconnected from your SSH session, then the
nohup command can come in handy.
This is a good example, this will run the nmap scan and then logout the user. When you re-connect, it will still be running.
nohup sudo nmap -A -T2 -P0 hackthissite.com -oN nmap-log.log &exit
So, this is a good way to run a command over SSH that will take a long time. The -oN nmap-log.log parameter to nmap will output the scan results into a file named nmap-log.log for later perusal when you log back in. Otherwise, the penetration tester would have to wait for ages whilst a long nmap scan completed. This is a very useful Linux tip and well worth knowing when the user is accessing a machine like Amazon AWS over an Internet connection and the connection is not always reliable.
This way, the user can run commands over a flaky Internet connection, and the command will still be running when the user is disconnected. This is why the Linux command line is so powerful.