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