Linux System Command 
  Update package information from all configured sources
  sudo apt-get update 
  
  Install the newest versions of all packages currently installed on the system from the sources
  sudo apt-get upgrade 
  
  
  To clean the apt cache, etc.
  sudo apt-get clean 
  
  sudo apt-get autoremove 
  
  List out all the network (socket) connections on a system
  netstat -ant 
  
  List out all processes from the Linux terminal on a system
  ps -aux 
  
   
  Add write permission to a file or directory
  sudo chmod a+w 'file or directory' 
  
  Copy files from local machine to remote machine
  scp PATH(local machine) USERNAME@IP:PATH(remote machine) 
  
AWS Command 
  Find bitnami application credentials(AWS lightsail)
  cat bitnami_application_password 
  
LAMP Command 
  Restart apache server
  sudo service apache2 restart