Have you ever wondered you can login to a server without entering any password ! Yes, it is possible - one such method is using SSH keys. Below procedure explains the steps how you can configure 2 servers to use SSH keys and enable password less login. This is also popularly known as SSH equivalence.Execute below steps on the source machine :
If ssh is not present, then please follow below steps.
1) Open ssh version 2 or higher must be installed on both the machines.
To check type this command on both the machines.
% rpm -qa | grep ssh
openssh-3.6.1p2-18
openssh-askpass-3.6.1p2-18
openssh-clients-3.6.1p2-18
openssh-server-3.6.1p2-18
openssh-askpass-gnome-3.6.1p2-18
2) Check the version of ssh using command.
% ssh -V
OpenSSH_3.6.1p2, SSH protocols 1.5/2.0, OpenSSL 0x0090701f
Make sure you are using ssh protocol 2 version.
3) Make sure the deamon process sshd is running on remote machine on
which you want to login without password.
To check this, use following command
% ps -ef | grep sshd
root 884 1 0 May14 ? 00:00:02 /usr/sbin/sshd
4) On the source machine , generate a pair of public/private key.
1. Firstly create the directory .ssh under user directory for example under /home/testuser.
Command : mkdir .ssh
Command : chmod 700 .ssh
Command : cd .ssh
2. Generate your public/private keys using ssh-keygen as follows.
Command : ssh-keygen -t dsa -f identity -b 1024
When it prompts to enter a passphrase , simply provide blank by pressing Enter Keys
3. Set permissions as give below.
Command : chmod 600 identity
Command : chmod 644 identity.pub
Command : cat identity.pub (Key would display in encypted form as below )
ssh-dss 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 testuser@shareolite
Now on the remote server :
a) Create the .ssh directory under /home/testuser2 if it does not exist
Command : cd /home/testuser2
Command : mkdir .ssh
Command : chmod 700 .ssh
Command : vi /home/testusers/.ssh/authorized_keys2
copy the contents of source machine identity.pub file
Command : chmod 644 /home/testuser2/.ssh/authorized_keys2
Now from source machine if you execute the below command , you should be able to login without prompting for any password
ssh testuser2@remoteserverIP
Example : ssh testuser2@172.10.89.2
You can now execute commands on remote server using this method without entering any password as shown in below example
ssh testuser2@remoteserverIP "linux command"
Example : ssh testuser2@172.10.89.2 "date"
Hope this is useful sometimes.