Servers Time Synchronization with ntpd (CentOS 5.5)

Servers Time Synchronization with ntpd (CentOS 5.5)

Ref: http://www.cyberciti.biz/faq/howto-install-ntp-to-synchronize-server-clock/

Install ntpd daemon:

yum install ntp

Configure ntpd for automatic startup:

/sbin/chkconfig ntpd on

Initial time synchronization:”

ntpdate pool.ntp.org

Start ntpd daemon:

/etc/init.d/ntpd start

Install this service on all your servers.

Configuration file looks like this:

/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

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 0.centos.pool.ntp.org

server 1.centos.pool.ntp.org

server 2.centos.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   # local clock

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