setup passphaseless ssh before installing hadoop on ubuntu
时间：2022-04-03 13:20
This can refer to hadoop main page below for setuping passphaseless ssh:
http://hadoop.apache.org/docs/r2.6.5/hadoop-project-dist/hadoop-common/SingleCluster.html
1) install ssh on ubuntu: sudo apt-get install ssh(ssh localhost)
2) ssh-keygen(or ssh-keygen -t rsa).
3) cd ~/.ssh
4) cat id_rsa.pub >> authorized_keys.
5) chmod og-wx authorized_keys(this step is optional).
