gistfile1.txt

1. ntpd update
$ sudo yum update ntp

2. ntpd stop 
$ sudo service ntpd stop

3. kernel retention time・clear frequency offset 
$ sudo ntptime -s 0 -f 0

4. change ntpd slew mode boot options 
$ sudo sed -i -e 's/OPTIONS="\(.*\)\-g"/OPTIONS="\1\-g \-x"/' /etc/sysconfig/ntpd

5. ntpd start 
$ sudo service ntpd start