先连上网,然后更换yum源

1. 新建的用户没有sudo权限，所以首先切换到root用户
su -
输入密码

2. 备份之前的yum源
mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup

3. 下载yum源centos6
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repo

4. 清理并生成缓存
yum clean all
yum makecache

安装ssh server

$ yum search ssh

$ yum install openssh-server

$ chkconfig --list sshd

sshd      0:off    1:off    2:on    3:on    4:on    5:on    6:off