Recently encountered a problem, because the problem of two servers of time, often causing the user logon problems because of the time difference error, repeatedly Baidu, finally compiled a modified linux timing synchronization operation (this method is suitable for server has its own time, not only limited reference)
First confirm whether we have the service installed ntp service
If not, you need to install ntp service
After installing ntp, edited ntp.conf
we /etc/ntp.conf
You can see the contents of the file
# 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 kod nomodify notrap nopeer noquery restrict -6 default kod 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 -6 ::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 127.0.0.1 #server 1.centos.pool.ntp.org #server 2.centos.pool.ntp.org #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 # Undisciplined Local Clock. This is a fake driver intended for backup # and when no outside source of synchronized time is available.
# local clock #fudge 127.127.1.0 stratum 10 # 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
You can see in the file 
modification marked out the ip address instead of their own time server address or domain name
Modified save and exit
Command line input
crontab -e
Setting the timing task, which is set here
* * */1 * * /usr/sbin/ntpdate 127.0.0.1 >> /home/logs/ntpd.log
Also modify ip address
and then create a log file folder used to store log
mkdir /home/logs
ok you're done, you can see a few minutes clip log files in the log file, the browser will find the time difference is not more than 0.01s. In general is good enough for the