ntp和ssh命令

1.配置ntp时间服务器，确保客户端主机能和服务主机同步时间

首先关闭防火墙、selinux：

[root@server ~]# systemctl  stop  firewalld
[root@server ~]# setenforce 0
[root@server ~]# getenforce
Permissive

第一步：在服务机中配置阿里云同步时间

[root@server ~]# vim  /etc/chrony.conf

 第二步：定位服务端，重启服务，判断是否同步

[root@server ~]# systemctl restart chronyd
[root@server ~]# chronyc sources -v

  .-- Source mode  '^' = server, '=' = peer, '#' = local clock.
 / .- Source state '*' = current best, '+' = combined, '-' = not combined,
| /             'x' = may be in error, '~' = too variable, '?' = unusable.
||                                                 .- xxxx [ yyyy ] +/- zzzz
||      Reachability register (octal) -.           |  xxxx = adjusted offset,
||      Log2(Polling interval) --.      |          |  yyyy = measured offset,
||                                \     |          |  zzzz = estimated error.
||                                 |    |           \
MS Name/IP address         Stratum Poll Reach LastRx Last sample               
===============================================================================
^* 203.107.6.88                  2   6    17     3  -1245us[-3233us] +/-   25ms
[root@server ~]# timedatectl status 
               Local time: 日 2023-03-19 17:13:59 CST
           Universal time: 日 2023-03-19 09:13:59 UTC
                 RTC time: 日 2023-03-19 09:13:59
                Time zone: Asia/Shanghai (CST, +0800)
System clock synchronized: yes
              NTP service: active
          RTC in local TZ: no

第三步：定位服务端，配置允许访问的主机ip并重启

[root@server ~]# vim /etc/chrony.conf 

[root@server ~]# systemctl restart chronyd

第四步：定位客户端，测试时间同步：

[root@node1 ~]# chronyc sources -v

  .-- Source mode  '^' = server, '=' = peer, '#' = local clock.
 / .- Source state '*' = current best, '+' = combined, '-' = not combined,
| /             'x' = may be in error, '~' = too variable, '?' = unusable.
||                                                 .- xxxx [ yyyy ] +/- zzzz
||      Reachability register (octal) -.           |  xxxx = adjusted offset,
||      Log2(Polling interval) --.      |          |  yyyy = measured offset,
||                                \     |          |  zzzz = estimated error.
||                                 |    |           \
MS Name/IP address         Stratum Poll Reach LastRx Last sample               
===============================================================================
^* 119.28.206.193                2   6   377    39  +1086us[  +79us] +/-   65ms
^+ 79.133.44.136                 1   6   377    36    -10ms[  -10ms] +/-   97ms
^+ stratum2-1.ntp.mow01.ru.>     2   6   377    10  +2463us[+2463us] +/-  101ms
^- time.cloudflare.com           3   6   177   101    +54ms[  +53ms] +/-  149ms
[root@node1 ~]# date
2023年 03月 19日 星期日 17:16:52 CST

2.配置ssh免密登陆，能够通过客户端主机通过redhat用户和服务端主机基于公钥验证方式进行远程连接

 第一步：创建用户

 第二步：定位客户端，制作秘钥并将公钥复制到服务端

[redhat@node1 root]$ ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/redhat/.ssh/id_rsa): 
Created directory '/home/redhat/.ssh'.
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/redhat/.ssh/id_rsa
Your public key has been saved in /home/redhat/.ssh/id_rsa.pub
The key fingerprint is:
SHA256:nfoBRGEjIjGVg7VBt14Z7K4UJKmqUk5Y3ITygCDBfCM redhat@node1
The key's randomart image is:
+---[RSA 3072]----+
|O.+B*oo.*.       |
|=Eo=*=.=.+       |
| =o+o+..+        |
|  = ...o.. .     |
| +    .oS o      |
|o o   . .o       |
|.+   . .. .      |
|o .   .  . .     |
|.         .      |
+----[SHA256]-----+
[redhat@node1 root]$ ssh-copy-id [email protected]
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/home/redhat/.ssh/id_rsa.pub"
The authenticity of host '192.168.125.128 (192.168.125.128)' can't be established.
ED25519 key fingerprint is SHA256:XwtjuqXGT6G23IUIRHYQTSzyZUUSMdJVGG4XyoO093A.
This key is not known by any other names
Are you sure you want to continue connecting (yes/no/[fingerprint])? 
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
The authenticity of host '192.168.125.128 (192.168.125.128)' can't be established.
ED25519 key fingerprint is SHA256:XwtjuqXGT6G23IUIRHYQTSzyZUUSMdJVGG4XyoO093A.
This key is not known by any other names
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
/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.

[redhat@node1 root]$ 

第二步：客户端测试