部署环境

创建普通用户：

  # tail -n2 /etc/passwd
  postfix:x:89:89::/var/spool/postfix:/sbin/nologin
  chrony:x:998:996::/var/lib/chrony:/sbin/nologin
  # useradd user01
  # tail -n2 /etc/passwd
  chrony:x:998:996::/var/lib/chrony:/sbin/nologin
  user01:x:1000:1000::/home/user01:/bin/bash

修改普通用户密码：

  # passwd user01
  更改用户 user01 的密码 。
  新的 密码：
  重新输入新的 密码：
  passwd：所有的身份验证令牌已经成功更新。
  # tail -n2 /etc/shadow
  chrony:!!:17747::::::
  user01:$6$gjFGJMEm$2JReki/pYBzsJqj0qkIExnEx7Q/u...xex3w/fxJ6JI05mOPMmLXf4QdsLvTBhfm5SnZnTetKAVtOkD2xfDnr1:17750:0:99999:7:::

所有服务器要求只能普通用户登录，root只能普通用户sudo:

更改配置文件，搜索Root那行更改如下内容：

  # vi /etc/ssh/sshd_config
  把#PermitRootLogin yes改为PermitRootLogin no禁止root远程登录，保存并退出

改完配置文件要重启服务：

  # systemctl restart sshd.service

密钥登录：

SSH登录是用的RSA非对称加密的，在SSH登录的时候就可以使用RSA密钥登录，SSH有专门创建SSH密钥的工具ssh-keygen。

执行命令ssh-keygen创建密钥对，执行过程中有交互过程，可以输入密钥密码也可以为空直接三次回车即可。

  [root@zyshanlinux-04 ~]# ssh-keygen  -t rsa
  Generating public/private rsa key pair.
  Enter file in which to save the key (/root/.ssh/id_rsa): 
  Enter passphrase (empty for no passphrase): 
  Enter same passphrase again: 
  Your identification has been saved in /root/.ssh/id_rsa.
  Your public key has been saved in /root/.ssh/id_rsa.pub.
  The key fingerprint is:
  SHA256:4odZd916XMzHfVl6wd18TsM/aaPzJX2znzIfN5N87pU root@zyshanlinux-04
  The key's randomart image is:
  +---[RSA 2048]----+
  |                 |
  |              o.o|
  |               =B|
  |             . OX|
  |      . S . . o*&|
  |     . = . .  +=O|
  |      + .    ooEX|
  |       .     oo+&|
  |              +*=|
  +----[SHA256]-----+
  ​

密钥对生成后，会在/root/.ssh/目录下多次两个文件id_rsa私钥和id_rsa.pub公钥

  [root@zyshanlinux-04 ~] # ls /root/.ssh
  id_rsa  id_rsa.pub

接着把生成的公钥拷贝到需要登录的远程服务器上，这里可以使用ssh-copy-id命令，这时需要目标服务器的登录密码

  [root@zyshanlinux-04 ~]# ssh-copy-id -i .ssh/id_rsa.pub [email protected]  ##该命令需要在根目录上执行，如果在非根目录上执行则是：ssh-copy-id -i ~/.ssh/id_rsa.pub [email protected]
  /usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: ".ssh/id_rsa.pub"
  /usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
  /usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
  [email protected]'s password: 
  ​
  Number of key(s) added: 1
  ​
  Now try logging into the machine, with:   "ssh '[email protected]'"
  and check to make sure that only the key(s) you wanted were added.
  ​

拷贝公钥完成后，远程连接目标服务器，这时就不需要登录密码

  [root@zyshanlinux-04 ~]# ssh '[email protected]'
  Last login: Tue Aug  7 21:13:09 2018 from 192.168.106.132
  [root@zyshanlinux-03 ~]#