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 Hardening Linux 

sample: Ubuntu 20.04
NOTE: it will be quite the same for the RedHAT, CentOS, etc
differs from [apt/yum] when invoking commands. 

1. update the host

# sudo apt update
# sudo apt upgrade

2. create a new user

# adduser [username]

3. add user to sudo group

# usermod -aG sudo [username]
flags: 
-a = append
-G = group

4. validate the access of the new user [login]
5. validate if the user is part of "sudo group"

# sudo whoami

>> ssh configuration

  6x1. lock root user for SSH login

  # sudo vi /etc/ssh/sshd_config
  
  6x2. find the following tag and change it to "no" [if not, add it]
  
  # PermitRootLogin no

  6x3. change port
  
  # Port 2222

  6x4. set max auth tries 

  # MaxAuthTries 5
  
  6x5. define the user accounts allowed to connect [add the line]
  
  # AllowUsers [username]

7. restart SSH service

# sudo service ssh restart

in progress...