when user login through terminal, automatically an email send to owner

$ sudo apt-get update
$ sudo apt install mailutils
$ sudo systemctl restart postfix

Put the following in /etc/profile:

if [ -n "$SSH_CLIENT" ]; then 
    TEXT="$(date): ssh login to ${USER}@$(hostname -f)" 
    TEXT="$TEXT from $(echo $SSH_CLIENT|awk '{print $1}')" 
    echo $TEXT|mail -s "ssh login" adityaypi@yahoo.com 
fi

How the script works

/etc/profile is executed at every login (for bash shell users). The if statement will only return true if the user has logged in via ssh, which in turn will cause the indented code block to be run.

Next, we then build the text of the message:

• $(date) will be replaced by the output of the date command
• ${USER} will be replaced by the user’s login name
• $(hostname -f) will be replaced by the full hostname of the system being logged into

The second TEXT line adds to the first, giving the IP address of the system this user is logging in from. Finally, the generated text is sent in an email to your address.

$ sudo /etc/init.d/ssh restart
$ sudo service ssh restart
$ sudo restart ssh
$ sudo systemctl restart ssh