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Tuesday, April 10, 2012

NTP server and client configuration (without security feature)

Before successfully install and start HBase, it is very important to make each nodes in hadoop cluster to sync time with each other as timestamp plays vital important roles in HBase. The following is my step to setup NTP in my Hadoop cluster.

install NTPD server

  1. #yum install ntp
  2. # chkconfig ntpd on
  3. # vi /etc/ntp.conf
    add the folowing lines in the file,
    #default is refuse all connections.
    restrict default ignore
    
    # allow hosts in LAN to sync time. 
    
    restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap
    
    # Use public servers from the pool.ntp.org project.
    server 0.centos.pool.ntp.org
    server 1.centos.pool.ntp.org
    server 2.centos.pool.ntp.org
    
    #allow uplevel server to comunicate with server.
    restrict 0.centos.pool.ntp.org nomodify notrap noquery
    restrict 1.centos.pool.ntp.org nomodify notrap noquery
    restrict 2.centos.pool.ntp.org nomodify notrap noquery
    
    # 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
    
    
  4. enable UDP at port number 123 for NTPD server
    # system-configure-firewal-tui
  5. ntpdate 0.centos.pool.ntp.org  (or ip address without prefix number)
  6. make sure ntpd server is running
    #service ntpd start
  7. check ntpd status
    ntpq -p
  8. check network interface status and see if ntpd is listening on port 123
    netstat -tupln

install ntp client



  1. # yum install ntp
  2. # chkconfig --list | grep ntpd
  3. chkconfig --del ntpd
  4. # cd /etc/cron.daily/
    or
    # cd /etc/cron.hourly/
  5. create file as below,
    # vi ntp.sh
    put command in ntp.sh
    #!/bin/bash /usr/sbin/ntpdate my.ntp.hostname
  6. make it as a executable
    # chmod 755 /etc/cron.daily/ntp.sh
  7. Finally restart the cron daemon.
    # service crond restart

However, it is better to use ntpd instead of ntpdate on "client" hosts


below is my example ntp.conf for "client" hosts.
# 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
server 192.168.1.138

#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
restrict 192.168.1.138 nomodify notrap noquery

# 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

# 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

# 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

# Enable writing of statistics records.
#statistics clockstats cryptostats loopstats peerstats

Below is my server ntpd.conf 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

restrict default ignore  //set default to refuse all accessing.

# 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 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
restrict 0.centos.pool.ntp.org notrap noquery
restrict 1.centos.pool.ntp.org notrap noquery
restrict 2.centos.pool.ntp.org notrap noquery


# 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

# 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

# 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

# Enable writing of statistics records.
#statistics clockstats cryptostats loopstats peerstats


https://bugzilla.redhat.com/show_bug.cgi?id=679537 http://hi.baidu.com/myiaas/item/bd7c84efa10bcb2a6cabb858 http://www.zimbio.com/Linux/articles/1dR6WZpCGW2/NTP+Sync+Startup+How+Linux+Howto+Redhat+CentOS http://www.centos.org/modules/newbb/viewtopic.php?topic_id=10410

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