CentOS: time syncronization in local network / setting timezone

http://hook.tistory.com/entry/RHEL-CentOS%EC%97%90%EC%84%9C-ntp-%EC%84%9C%EB%B2%84-%EC%84%A4%EC%A0%95%ED%95%98%EA%B8%B0%EC%82%AC%EC%84%A4%EB%A7%9D-%EB%82%B4%EB%B6%80-%EC%84%9C%EB%B2%84%EB%93%A4%EC%9D%98-%EC%8B%9C%EA%B0%84-%EB%8F%99%EA%B8%B0%ED%99%94


server1: x.y.w.z1
server2: x.y.w.z2
server3: x.y.w.z3

all servers
# yum install ntp -y

server1
# vi /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
restrict x.y.w.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
server x.y.w.z1

#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

# /etc/init.d/ntpd start
# chkconfig ntpd on
# ps -ef | grep ntpd
# ntpq -pn

server[n]
# ntpdate -u x.y.w.z1

http://whomwah.com/2008/10/01/setting-the-timezone-on-centos/

#
# this is not correct for me
#
$ date
Wed Oct  1 07:43:58 CDT 2008
#
# to fix it
#
$ sudo rm /etc/localtime
$ sudo ln -s /usr/share/zoneinfo/America/New_York /etc/localtime
#
# now check it's ok
#
$ date
Wed Oct  1 12:42:33 GMT 2008