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.
   • RHEL compatible:

     yum install ntp

   • SLES:

     zypper install ntp

   • Ubuntu:

     apt-get install ntp

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

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

3. Start the NTP service:
   • RHEL 7 Compatible:

     sudo systemctl start ntpd

   • RHEL 6 Compatible, SLES, Ubuntu:

     sudo service ntpd start

4. Configure the NTP service to run at boot:
   • RHEL 7 Compatible:

     sudo systemctl enable ntpd

   • RHEL 6 Compatible, SLES, Ubuntu:

     chkconfig ntpd on

5. Synchronize the node.

   ntpdate -u <ntp_server>

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

   hwclock --systohc