发现REDHAT LINUX服务器时间慢了5分钟--因为没有配置NTP时钟同步。上面有应用在运行，不能用ntpdate来强行修改时间。

查ntpd的manual，发现缺省的/etc/ntpd.conf的配置无需修改，直接启动ntpd服务即可实现时间的逐渐同步。

[root@host ~]# date
Sat Sep 27 17:14:31 CST 2008
[root@host ~]# ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
+time-a.nist.gov .ACTS. 1 u 62 64 317 278.725 918977. 45.220
*time-b.nist.gov .ACTS. 1 u 64 64 377 287.306 918968. 44.043
+time.nist.gov .ACTS. 1 u 57 64 377 250.725 919020. 25.743
-207.46.232.182 138.23.180.126 3 u 57 64 377 229.390 919032. 35.858
LOCAL(0) LOCAL(0) 10 l 9 64 377 0.000 0.000 0.001

但是大约半小时后，系统时间被突然修改为正确时间，也就是说时间不是逐渐同步，而是快速同步的 :(

[root@host ~]# ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
time-a.nist.gov .ACTS. 1 u 47 64 33 278.758 105.577 16.650
*time-b.nist.gov .ACTS. 1 u 46 64 177 287.310 127.448 40.466
+time.nist.gov .ACTS. 1 u 47 64 173 250.667 86.182 31.323
+207.46.232.182 138.23.180.126 3 u 45 64 177 229.337 101.141 24.597
LOCAL(0) LOCAL(0) 10 l 62 64 177 0.000 0.000 0.001
[root@host ~]# date; hwclock
Sat Sep 27 17:48:45 CST 2008
Sat 27 Sep 2008 05:18:45 PM CST -0.016026 seconds