SSH / SCP key authentication

Many time bash scrip demands scp. OR you may not wish to enter password every time you access remote server.

Generate key for local system.

ssh-keygen -t rsa

Copy key to remote server.

ssh-copy-id -i /root/.ssh/id_rsa.pub root@192.168.1.1

Now you can ssh / scp without entering password.
For old system not equipped with ssh-copy-id

ssh-keygen -t rsa
scp ~/.ssh/id_rsa.pub root@192.168.1.1:
ssh root@192.168.1.1 ‘cat id_rsa.pub >> .ssh/authorized_keys’