立即同步时间的坏处，影响某些计划任务执行
一、立即同步时间
方法一：
ntpdate ntp.aliyun.com方法二：重启ntp服务
方法三：重启chrony服务
二、查看ntp和chrony状态
[root@textbox ~]# chronyc sources -v
210 Number of sources = 1
.-- Source mode '^' = server, '=' = peer, '#' = local clock.
/ .- Source state '*' = current synced, '+' = combined , '-' = not combined,
| / '?' = unreachable, 'x' = time may be in error, '~' = time too variable.
|| .- 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
===============================================================================
^* localhost 3 6 17 2 +62us[ +661us] +/- 88ms
[root@textbox ~]#[root@textbox ~]# ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
*localhost 119.28.206.193 3 u 41 64 177 0.784 1.195 3656236三、ntp做服务端的设置
#注释原来的ntp服务器，原来的ntp服务器都是centos.org美国的
[root@textbox ~]# sed '/^server/s/^/#/' /etc/ntp.conf -i
#添加两个aliyun的
[root@textbox ~]# sed '1a server ntp.aliyun.com iburst' /etc/ntp.conf -i
[root@textbox ~]# sed '1a server ntp1.aliyun.com iburst' /etc/ntp.conf -i
#重启服务
[root@textbox ~]# systemctl restart ntpd
#ntp就这么简单，就可以当服务器使用了
[root@textbox ~]# ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
+120.25.115.20 10.137.53.7 2 u 4 64 17 42.560 -8.795 6.944
*203.107.6.88 100.107.25.114 2 u 4 64 17 15.542 -7.021 6.460
#123端口，udp
[root@textbox ~]# ss -lutnp | grep ntp
udp UNCONN 0 0 192.168.38.140:123 *:* users:(("ntpd",pid=61668,fd=19))
udp UNCONN 0 0 127.0.0.1:123 *:* users:(("ntpd",pid=61668,fd=18))
udp UNCONN 0 0 *:123 *:* users:(("ntpd",pid=61668,fd=16))
udp UNCONN 0 0 fe80::69d0:5288:fda9:93ae%ens33:123 :::* users:(("ntpd",pid=61668,fd=21))
udp UNCONN 0 0 ::1:123 :::* users:(("ntpd",pid=61668,fd=20))
udp UNCONN 0 0 :::123 :::* users:(("ntpd",pid=61668,fd=17))
#用另一台服务器测试
[root@linux5 ~]# ntpdate 192.168.38.140
5 Sep 09:17:25 ntpdate[28423]: adjust time server 192.168.38.140 offset -0.007790 sec四、chrony服务端配置
设置项比ntp多
[root@imooc-nginx ~]# sed '/^server/s/^/#/' /etc/chrony.conf -i
[root@imooc-nginx ~]# sed '1a server ntp.aliyun.com iburst' /etc/chrony.conf -i
[root@imooc-nginx ~]# sed '1a server 0.cn.pool.ntp.org iburst' /etc/chrony.conf -i
[root@imooc-nginx ~]# sed '1a server ntp1.aliyun.com iburst' /etc/chrony.conf -i
#即使当前时服务器未与指定ntp完成时间同步，照样提供服务
[root@imooc-nginx ~]# sed '1a local stratum 10' /etc/chrony.conf -i
#允许哪些服务器同步
[root@imooc-nginx ~]# sed '1a allow 192.168.0.0/16' /etc/chrony.conf -i
[root@imooc-nginx ~]# systemctl restart chronyd
[root@imooc-nginx ~]# systemctl enable chronyd
#查看chronyd状态
[root@imooc-nginx ~]# chronyc sources -v
210 Number of sources = 3
.-- Source mode '^' = server, '=' = peer, '#' = local clock.
/ .- Source state '*' = current synced, '+' = combined , '-' = not combined,
| / '?' = unreachable, 'x' = time may be in error, '~' = time too variable.
|| .- 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
===============================================================================
^+ 120.25.115.20 2 6 17 4 +766us[ +591us] +/- 21ms
^- 111.230.189.174 2 6 17 4 +98us[ +98us] +/- 49ms
^* 203.107.6.88 2 6 17 4 -187us[ -361us] +/- 16ms
#测试
[root@textbox ~]# ntpdate 192.168.38.154
5 Sep 09:33:25 ntpdate[61810]: adjust time server 192.168.38.154 offset -0.010546 sec五、自动同步时间两种方式
1、ntpdate ntp.aliyun.com写入计划任务，每小时同步一次
2、所有服务器chrony都开启，其中一台做时间服务器，其他服务器的server都指向它
六、设置时区
[root@textbox ~]# timedatectl set-timezone Asia/Shanghai另外有需要云服务器可以了解下创新互联cdcxhl.cn，海内外云服务器15元起步，三天无理由+7*72小时售后在线，公司持有idc许可证，提供“云服务器、裸金属服务器、高防服务器、香港服务器、美国服务器、虚拟主机、免备案服务器”等云主机租用服务以及企业上云的综合解决方案，具有“安全稳定、简单易用、服务可用性高、性价比高”等特点与优势，专为企业上云打造定制，能够满足用户丰富、多元化的应用场景需求。
