Enterprise Linux: Time Synchronization

# Manual steps

[root@linux64-server ~]# service ntpd status

ntpd (pid  3827) is running...

[root@linux64-server ~]# ntpdate pool.ntp.org

19 Jan 14:42:12 ntpdate[4521]: the NTP socket is in use, exiting

[root@linux64-server ~]# kill -9 3827

[root@linux64-server ~]# ntpdate pool.ntp.org

17 Jun 10:34:50 ntpdate[4523]: step time server 209.167.68.100 offset 13027946.745300 sec

[root@linux64-server ~]# date

Mon Jun 17 10:34:58 EDT 2012

# GUI configuration

# Command line configuration

1.       edit /etc/ntp.conf

# 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

# 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 0.rhel.pool.ntp.org

server 1.rhel.pool.ntp.org

server 2.rhel.pool.ntp.org

#broadcast 192.168.1.255 key 42         # broadcast server

#broadcastclient                        # broadcast client

#broadcast 224.0.1.1 key 42             # multicast server

#multicastclient 224.0.1.1              # multicast client

#manycastserver 239.255.254.254         # manycast server

#manycastclient 239.255.254.254 key 42  # manycast client

# Undisciplined Local Clock. This is a fake driver intended for backup

# and when no outside source of synchronized time is available.

server 127.127.1.0

fudge   127.127.1.0 stratum 10

# Drift file.  Put this in a directory which the daemon can write to.

# No symbolic links allowed, either, since the daemon updates the file

# by creating a temporary in the same directory and then rename()'ing

# it to the file.

driftfile /var/lib/ntp/drift

# Key file containing the keys and key identifiers used when operating

# with symmetric key cryptography.

keys /etc/ntp/keys

# Specify the key identifiers which are trusted.

#trustedkey 4 8 42

# Specify the key identifier to use with the ntpdc utility.

#requestkey 8

# Specify the key identifier to use with the ntpq utility.

#controlkey 8

restrict 0.rhel.pool.ntp.org mask 255.255.255.255 nomodify notrap noquery

restrict 1.rhel.pool.ntp.org mask 255.255.255.255 nomodify notrap noquery

restrict 2.rhel.pool.ntp.org mask 255.255.255.255 nomodify notrap noquery

2. add below contents into /etc/ntp/step-tickers

0.rhel.pool.ntp.org

1.rhel.pool.ntp.org

2.rhel.pool.ntp.org

3.       service /etc/ntpd restart