上QQ阅读APP看书，第一时间看更新
Getting ready
Connect to both centos1 and centos2. Doing this from outside (in separate windows, and using vagrant ssh) is best:
$ vagrant ssh centos1
$ vagrant ssh centos2
Place your Terminal windows side by side for easy viewing.
There is a chance that you will break SSH access to your server in this section, which is why I advise using Vagrant for your testing. If you do make a mistake, don't worry – simply destroy your VMs and start again.