We have several CENTOS 4 and 5 servers. ALL CENTOS servers have NTP setup to sync time server. Several days ago due to power outage all servers are reboot. Due to DNS server did NOT up quickly, CENTOS servers start up and can NOT find time server. For CENTOS 5.X servers, it did quickly resync to time server after 30 minutes. For CENTOS 4.X servers, it have been 3 days still NOT sync to time server. I know I can run "service ntpd restart" to force server sync to time server, but I like to know how long it take for CENTOS 4.X automatic resync to time server. Thanks.