CentOS 7 学习笔记（一）时间管理
1 获取当前时间
[root@limt01 ~]# date 2015年 05月 22日 星期五 01:30:50 CST
2 获取当前日期
[root@limt01 ~]# date "+%Y%m%d" 20150522
3 获取三天之前日期
[root@limt01 ~]# date -d "-3 days" "+%Y%m%d" 20150519
4 获取三天之后的日期
[root@limt01 ~]# date -d "+3 days" "+%Y%m%d" 20150525
5 获得月末日期
[root@limt01 ~]# cal|xargs|awk '{ print $NF }'|sed 's/ //g' 31
6 查看时区
[root@limt01 ~]# date -R Fri, 22 May 2015 01:45:26 +0800 （+0800 表示东八区）
7 设置时间
[root@limt01 ~]# date 0522082515 2015年 05月 22日 星期五 08:25:00 CST 或者 [root@limt01 ~]# date -s "2015-05-22 08:25:22" 2015年 05月 22日 星期五 08:25:22 CST [root@limt01 ~]# hwclock -r //读入BIOS时间 2015年05月22日 星期五 01时50分54秒 -0.726681 秒 [root@limt01 ~]# hwclock -w //向BIOS写入时间 [root@limt01 ~]# hwclock -r 2015年05月22日 星期五 08时26分08秒 -0.582655 秒
8 检测时区配置
[root@limt01 sysconfig]# timedatectl Local time: 五 2015-05-22 08:30:02 CST Universal time: 五 2015-05-22 00:30:02 UTC RTC time: 五 2015-05-22 00:29:44 Timezone: Asia/Shanghai (CST, +0800) NTP enabled: yes NTP synchronized: no RTC in local TZ: no DST active: n/a
9 列出所有时区
[root@limt01 sysconfig]# timedatectl list-timezones Africa/Abidjan Africa/Accra Africa/Addis_Ababa Africa/Algiers Africa/Asmara Africa/Bamako Africa/Bangui Africa/Banjul Africa/Bissau Africa/Blantyre Africa/Brazzaville
10 设置时区
[root@limt01 sysconfig]# timedatectl set-timezone Asia/Shanghai （设置系统时区为上海） [root@limt01 sysconfig]# timedatectl set-local-rtc 0 # 将硬件时钟调整为与本地时钟一致, 0 为设置为 UTC 时间
11 NTP服务（端口123）
/usr/sbin/ntpdate xxx.xxx.xxx.xxx 手工与指导ntp服务器同步时间
NTP服务进程：
[root@limt01 ntp]# ps -ef|grep ntp|grep -v grep ntp 4304 1 0 08:32 ? 00:00:00 /usr/sbin/ntpd -u ntp:ntp -g
启动NTP服务：
[root@limt01 ntp]# systemctl start ntpd.service [root@limt01 ntp]# systemctl status ntpd.service ntpd.service - Network Time Service Loaded: loaded (/usr/lib/systemd/system/ntpd.service; enabled) Active: active (running) since 五 2015-05-22 08:44:05 CST; 3s ago Process: 4398 ExecStart=/usr/sbin/ntpd -u ntp:ntp $OPTIONS (code=exited, status=0/SUCCESS) Main PID: 4399 (ntpd) CGroup: /system.slice/ntpd.service └─4399 /usr/sbin/ntpd -u ntp:ntp -g 5月 22 08:44:05 limt01 ntpd[4399]: Listen and drop on 1 v6wildcard :: UDP 123 5月 22 08:44:05 limt01 ntpd[4399]: Listen normally on 2 lo 127.0.0.1 UDP 123 5月 22 08:44:05 limt01 ntpd[4399]: Listen normally on 3 eno16777736 192.168.1.104 UDP 123 5月 22 08:44:05 limt01 ntpd[4399]: Listen normally on 4 lo ::1 UDP 123 5月 22 08:44:05 limt01 ntpd[4399]: Listen normally on 5 eno16777736 fe80::20c:29ff:fe38:2d00 UDP 123 5月 22 08:44:05 limt01 ntpd[4399]: Listening on routing socket on fd #22 for interface updates 5月 22 08:44:05 limt01 ntpd[4399]: 0.0.0.0 c016 06 restart 5月 22 08:44:05 limt01 ntpd[4399]: 0.0.0.0 c012 02 freq_set kernel 0.000 PPM 5月 22 08:44:05 limt01 ntpd[4399]: 0.0.0.0 c011 01 freq_not_set 5月 22 08:44:06 limt01 ntpd[4399]: 0.0.0.0 c614 04 freq_mode
ntpdate 与 ntpd 不能同时使用
查看NTP同步状态：
[root@limt01 ntp]# /usr/sbin/ntpq -p remote refid st t when poll reach delay offset jitter ============================================================================== +news.neu.edu.cn 236.43.203.76 2 u 67 64 3 16.655 7.426 1.443 *dns2.synet.edu. 202.118.1.46 2 u 2 64 3 15.917 8.520 1.687
配置文件/etc/ntp.conf
[root@limt01 ntp]# less /etc/ntp.conf # For more information about this file, see the man pages # ntp.conf(5), ntp_acc(5), ntp_auth(5), ntp_clock(5), ntp_misc(5), ntp_mon(5). driftfile /var/lib/ntp/drift # Permit time synchronization with our time source, but do not # permit the source to query or modify the service on this system. restrict default nomodify notrap nopeer noquery # Permit all access over the loopback interface. This could # be tightened as well, but to do so would effect some of # the administrative functions. restrict 127.0.0.1 restrict ::1 # Hosts on local network are less restricted. #restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap # Use public servers from the pool.ntp.org project. # Please consider joining the pool (http://www.pool.ntp.org/join.html). server 0.centos.pool.ntp.org iburst server 1.centos.pool.ntp.org iburst server 2.centos.pool.ntp.org iburst server 3.centos.pool.ntp.org iburst #broadcast 192.168.1.255 autokey # broadcast server #broadcastclient # broadcast client #broadcast 224.0.1.1 autokey # multicast server #multicastclient 224.0.1.1 # multicast client #manycastserver 239.255.254.254 # manycast server #manycastclient 239.255.254.254 autokey # manycast client # Enable public key cryptography. #crypto includefile /etc/ntp/crypto/pw # Key file containing the keys and key identifiers used when operating # with symmetric key cryptography. keys /etc/ntp/keys # Specify the key identifiers which are trusted. #trustedkey 4 8 42 # Specify the key identifier to use with the ntpdc utility. #requestkey 8 # Specify the key identifier to use with the ntpq utility. #controlkey 8 # Enable writing of statistics records. #statistics clockstats cryptostats loopstats peerstats # Disable the monitoring facility to prevent amplification attacks using ntpdc # monlist command when default restrict does not include the noquery flag. See # CVE-2013-5211 for more details. # Note: Monitoring will not be disabled with the limited restriction flag. disable monitor
