record save here first
[root@hadoop .ssh]# ssh-keygen -t rsa -P ‘‘
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa): id_rsa
Your identification has been saved in id_rsa.
Your public key has been saved in id_rsa.pub.
The key fingerprint is:
5c:9a:67:12:49:6d:2d:ce:7e:da:fc:e3:ff:df:e5:58 root@hadoop
[root@hadoop .ssh]# ls
backup id_rsa id_rsa.pub known_hosts
[root@hadoop .ssh]# cp id_rsa.pub authorized_keys
[root@hadoop .ssh]# ls
authorized_keys backup id_rsa id_rsa.pub known_hosts
[root@hadoop .ssh]# start-all.sh
starting namenode, logging to /usr/local/hadoop/libexec/../logs/hadoop-root-namenode-hadoop.out
localhost: starting datanode, logging to /usr/local/hadoop/libexec/../logs/hadoop-root-datanode-hadoop.out
localhost: starting secondarynamenode, logging to /usr/local/hadoop/libexec/../logs/hadoop-root-secondarynamenode-hadoop.out
starting jobtracker, logging to /usr/local/hadoop/libexec/../logs/hadoop-root-jobtracker-hadoop.out
localhost: starting tasktracker, logging to /usr/local/hadoop/libexec/../logs/hadoop-root-tasktracker-hadoop.out
[root@hadoop .ssh]#
原文：http://www.cnblogs.com/fjsnail/p/4331250.html