HowTo: Password lesslogin in linux.

Password less logins allow you get get into the server even the password has been changed or expired ,

It can be achieve by single unix command you can use either this or the detailed steps given below. It will prompt password for server2,  once it is over the next login will be the password less

 [root@srv-51 ~]$ ssh-copy-id -i ~/.ssh/id_rsa.pub  syncfuser@192.168.1.52

Detailed steps :

1, Generate public key on server-1, ignore this step if it is already exist

 [root@srv-51 ~]$ ssh-keygen
 Generating public/private rsa key pair.
 Enter file in which to save the key (/root/.ssh/id_rsa):
 Created directory '/root/.ssh'.
 Enter passphrase (empty for no passphrase):
 Enter same passphrase again:
 Your identification has been saved in /root/.ssh/id_rsa.
 Your public key has been saved in /root/.ssh/id_rsa.pub.
 The key fingerprint is:
 8f:99:9f:8f:ba:bf:15:ca:6b:1f:83:06:a2:1a:9c:59 root@srv-51
 The key's randomart image is:
 +--[ RSA 2048]----+
 | |
 | |
 | |
 | |
 | E . S . |
 | . + . . B o . |
 | = . + * + |
 | o o.= o |
 | . o=B+o |
 +-----------------+

3, Grab the key and add it in the authorized_keys file in server2

[root@srv-51 ~]# cat ~/.ssh/id_rsa.pub
 ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEAz9iTxsWIYZyLtGN47MQZkSrPqXoGwATAKD/ZqIyemFRvKnlkSllkEEQ7+MlMstz6HvONfTJuJROegELqTIA7PoR43LTTKw7zfqJtt1J4fUH/6mbYlB5bedXtl/7L9auRYr276d04CFUCKfINEG4KJXYlbuSM8Mr5ZiUvLCkiu4Jx77DSy0iWaDa90C6cEbl1vRX9yl1pdWQbAMuazYLfiDPOnbqb7JtcI9du5bNEuFuA26VahaYbaYtXFnKBbKrCUMzTHT2uuNesYpckUHT4f0T1fU9qNsAYBlyQBgMIu/2qdJ+Y8luMVCkydXx8ZJmSTmAp+yR+qaZDYCqujrvjdQ== root@localhost.localdomain

4, Server2 authorized_keys key entry is looks like this

[root@srv-52 ~]# cat /home/syncfuser/.ssh/authorized_keys
 ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEAz9iTxsWIYZyLtGN47MQZkSrPqXoGwATAKD/ZqIyemFRvKnlkSllkEEQ7+MlMstz6HvONfTJuJROegELqTIA7PoR43LTTKw7zfqJtt1J4fUH/6mbYlB5bedXtl/7L9auRYr276d04CFUCKfINEG4KJXYlbuSM8Mr5ZiUvLCkiu4Jx77DSy0iWaDa90C6cEbl1vRX9yl1pdWQbAMuazYLfiDPOnbqb7JtcI9du5bNEuFuA26VahaYbaYtXFnKBbKrCUMzTHT2uuNesYpckUHT4f0T1fU9qNsAYBlyQBgMIu/2qdJ+Y8luMVCkydXx8ZJmSTmAp+yR+qaZDYCqujrvjdQ== root@localhost.localdomain

Finally output will be like this

 [root@srv-51 ~]# ssh syncfuser@192.168.1.52
 Last login: Wed Jun 25 17:08:25 2014 from 192.168.1.51
 [syncfuser@srv-52 ~]$

Now server1 root user can enter password less to the syncfuser on server2. 🙂