configure passphraseless SSH login among CentOS servers

1. wget http://pkgs.repoforge.org/rpmforge-release-0.5.2-2.el5.rf.x86_64.rpm
2. wget http://apt.sw.be/RPM-GPG-KEY.dag.txt
3. rpm -K rpmforge-release-0.5.2-2.el6.rf.x86_64.rpm
4. rpm -ivh rpmforge-release-0.5.2-2.el6.rf.x86_64.rpm
5. vi /etc/yum.repos.d/rpmforge.repo
   add “priority=3″ or other right priority number after “enabled = 1″
6. yum repolist
7. yum install keychain
8. ssh-keygen -t dsa
9. chmod 755 .ssh
10. scp ~/.ssh/id_dsa.pub user@remotehost:.ssh/authorized_keys
    Or:
    cat ~/.ssh/id_dsa.pub | ssh hadoopuser@remotehost "cat - >> ~/.ssh/authorized_keys"
11. chmod 600 ~/.ssh/authorized_keys
12. vi .bash_profile
    add following commands:
    /usr/bin/keychain -q $HOME/.ssh/id_dsa
    source $HOME/.keychain/$HOSTNAME-sh
13. Logout and login. password for key files is asked and will be asked at first time login only. or run command source .bash_profile 
14. run ssh among servers without being asked for password

http://www.cyberciti.biz/faq/ssh-password-less-login-with-dsa-publickey-authentication/ http://www.ehowstuff.com/how-to-configure-rpmforge-repository-on-centos-6-3/ http://www.cyberciti.biz/faq/ssh-passwordless-login-with-keychain-for-scripts/