Linux上实现ssh免密码登陆远程服务器
0.说明
平常使用ssh登陆远程服务器时，都需要使用输入密码，希望可以实现通过密钥登陆而免除输入密码，从而可以为以后实现批量自动部署主机做好准备。
环境如下：
| IP地址 | 操作系统 | |
| 服务器端 | 10.0.0.128/24 | CentOS 6.5 x86 |
| 客户端 | 10.0.0.129/24 | Ubuntu 16.04 x86 |
1.客户端生成密钥对
生成密钥对：
xpleaf@leaf:~$ ssh-keygen -t rsa -b 2048 Generating public/private rsa key pair. Enter file in which to save the key (/home/xpleaf/.ssh/id_rsa): Created directory '/home/xpleaf/.ssh'. Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /home/xpleaf/.ssh/id_rsa. Your public key has been saved in /home/xpleaf/.ssh/id_rsa.pub. The key fingerprint is: SHA256:eLssyXJLzUCfSN5mu6nqNH9dB/gOyXSvWBwQdNssIYE xpleaf@leaf The key's randomart p_w_picpath is: +---[RSA 2048]----+ | o=oo | | E .o = | | o oo o | | + = .o +. | | = So = + | | B o+ = o | | o...=. * o | | ..+=..+o o | | .o++== | +----[SHA256]-----+
查看生成的密钥对：
xpleaf@leaf:~$ ls .ssh id_rsa id_rsa.pub # id_rsa为私钥，这个一般需要保密；id_rsa.pub为公钥，这个可以公开。
2.上传公钥到服务器端
使用scp命令操作：
xpleaf@leaf:~$ scp .ssh/id_rsa.pub root@10.0.0.128:/root The authenticity of host '10.0.0.128 (10.0.0.128)' can't be established. RSA key fingerprint is SHA256:0Tpm11wruaQXyvOfEB1maIkEwxmjT2AklWb198Vrln0. Are you sure you want to continue connecting (yes/no)? yes Warning: Permanently added '10.0.0.128' (RSA) to the list of known hosts. root@10.0.0.128's password: id_rsa.pub 100% 393 0.4KB/s 00:00
3.服务器端操作
把从客户端传来的公钥添加到.ssh/authorized_keys中：
[root@leaf ~]# cat id_rsa.pub >> .ssh/authorized_keys [root@leaf ~]# chmod 600 .ssh/authorized_keys # authorized_keys的权限需要为600
修改ssh配置文件/etc/ssh/sshd_config，找到下面一行：
PubkeyAuthentication no
修改为：
PubkeyAuthentication yes
4.测试
在客户端上使用密钥登陆到服务器上：
xpleaf@leaf:~$ ssh -i .ssh/id_rsa root@10.0.0.128 Last login: Tue May 9 15:14:01 2017 from 10.0.0.129 [root@leaf ~]#
5.注意事项
在服务器端需要把selinux关闭，否则最后无法使用密钥进行远程登陆；
客户端使用scp命令时，在服务器端也需要安装ssh客户端，否则无法把公钥上传到服务器端，另外也可以使用ssh-copy-id root@10.0.0.128来代替scp操作（这样在服务器端也不需要执行创建.ssh目录等这些操作，即相当于该命令可以一步帮我们完成密钥的上传与配置工作）；
