To add any user to do ssh login in Linux

Edit (as root) /etc/ssh/sshd_config. Append the following to it:

Port 1234
PermitRootLogin no
AllowUsers testusr

It will permit root user to login ssh but only allow the  "testusr" to login ssh.
If you want allow root ,




PermitRootLogin yes


Then restart ssh


service ssh restart