CDH requires that you configure the Network Time Protocol (NTP) service on each machine in your cluster. To start NTP and configure it to run automatically on reboot, perform the following steps on each node in your cluster.

1. Install NTP.
   • For RHEL, CentOS, and Oracle:

     yum install ntp

   • For SLES:

     zypper install ntp

   • For Debian and Ubuntu:

     apt-get install ntp

2. Open the /etc/ntp.conf file and add NTP servers, as in the following example.

   server 0.pool.ntp.org
   server 1.pool.ntp.org
   server 2.pool.ntp.org

3. Save and close the file.
4. Configure the NTP service to run at reboot.

   chkconfig ntpd on

5. Start the NTP service.

   service ntpd start

6. Synchronize the node.

   ntpdate -u <your_ntp_server>

7. Synchronize the system clock (to prevent synchronization problems).

   hwclock --systohc