当服务器的时间不对的时候，可以使用ntpdate工具来校正时间。
安装：yum install ntpdate
ntpdate简单用法：
# ntpdate ip
# ntpdate 210.72.145.44
以下是一些可用的NTP服务器地址：
| Name | IP | Location |
| 210.72.145.44 | 210.72.145.44 | 中国（国家授时中心） |
| 133.100.11.8 | 133.100.11.8 | 日本（福冈大学） |
| time-a.nist.gov | 129.6.15.28 | NIST,Gaithersburg,Maryland |
| time-b.nist.gov | 129.6.15.29 | NIST,Gaithersburg,Maryland |
| time-a.timefreq.bldrdoc.gov | 132.163.4.101 | NIST,Boulder,Colorado |
| time-b.timefreq.bldrdoc.gov | 132.163.4.102 | NIST,Boulder,Colorado |
| time-c.timefreq.bldrdoc.gov | 132.163.4.103 | NIST,Boulder,Colorado |
| utcnist.colorado.edu | 128.138.140.44 | UniversityofColorado,Boulder |
| time.nist.gov | 192.43.244.18 | NCAR,Boulder,Colorado |
| time-nw.nist.gov | 131.107.1.10 | Microsoft,Redmond,Washington |
| nist1.symmetricom.com | 69.25.96.13 | Symmetricom,SanJose,California |
| nist1-dc.glassey.com | 216.200.93.8 | Abovenet,Virginia |
| nist1-ny.glassey.com | 208.184.49.9 | Abovenet,NewYorkCity |
| nist1-sj.glassey.com | 207.126.98.204 | Abovenet,SanJose,California |
| nist1.aol-ca.truetime.com | 207.200.81.113 | TrueTime,AOLfacility,Sunnyvale,California |
| nist1.aol-va.truetime.com | 64.236.96.53 | TrueTime,AOLfacility,Virginia |