Basic Linux Commands




see directory items

zipping & unzipping

System info

  • hmesg
  • To Know PCI device information
  • To know CPU information
  • To know how many disk/drives present in system
  • To know how much disk space used
    df -H
  • How much RAM present /used/free
    free -m

This will show in megabyte. -g can be used for gigabyte & -k can be used for killobyte.

Network Tools

  • To know which services using which ports
cat /etc/services
  • How to check if a port is in use on Linux
sudo lsof -i -P -n | grep LISTEN
sudo netstat -tulpn | grep LISTEN
sudo ss -tulpn | grep ':22'
  • How can you find out which process is listening on a port on Linux

sudo netstat -tulpn | grep :443
sudo ss -tulpn | grep ':22'


  • -t : Display TCP sockets/port
  • -u : Show UDP sockets/port
  • -l : See only listening sockets i.e. open port
  • -p : Also display process name that opened port/socket
  • -n : View addresses and port numbers in a numerical format. Do not use DNS to resolve names.

How to use Grep

Process Monitoring

  • PS
  • kill
  • top
  • stop

Spatial commands

  • cat
  • clear
  • less
  • head
  • tail
  • wc
  • chown
  • chmod

Manage users