Setting custom NTP servers on the AWS Transform discovery tool

When deploying the new AWS Transform discovery tool, NTP is automatically configured to use Amazon's NTP pools:

0.amazon.pool.ntp.org
1.amazon.pool.ntp.org
2.amazon.pool.ntp.org
3.amazon.pool.ntp.org

You may have a security policy requiring internal NTP, or you may want to completely block internet access. This post shows you how to reconfigure the VM for a custom NTP server.

Prerequisites

This article assumes that you can navigate the Linux command-line.

Deploy the OVA appliance using the Deploy the discovery tool section of the setup instructions.

Procedure

1. Access the deployed VM's console using the Accessing the discovery tool VM section of the setup instructions.

2. Edit the chrony config file. This example uses the vi editor, but nano is also available.

   discovery> sudo vi /etc/chrony.conf

3. Comment out the line sourcedir /run/chrony.d, then save the file.

   # Use NTP servers from DHCP.
   # sourcedir /run/chrony.d

4. Edit the chrony sources file

   discovery> sudo vi /etc/chrony.d/ntp-pool.sources

5. Comment out the 4 Amazon pools, then add your custom NTP servers. This example uses the server directive to point to 1 specific NTP server. You can add an arbitrary number of server directives. If you have internal pools instead, you use the pool directive. When finished, save the file.

   # pool 0.amazon.pool.ntp.org iburst maxsources 1
   # pool 1.amazon.pool.ntp.org iburst maxsources 1
   # pool 2.amazon.pool.ntp.org iburst maxsources 2
   # pool 3.amazon.pool.ntp.org iburst maxsources 1
   server 192.168.103.10 iburst

6. Add the chrony configured semaphore file.

   discovery> sudo touch /run/chrony.d/.configured

7. Restart the chrony service

   discovery> sudo systemctl restart chronyd

8. Verify NTP sources

   discovery> sudo chronyc sources
   MS Name/IP address         Stratum Poll Reach LastRx Last sample
   ===============================================================================
   ^* 192.168.103.10                2   6    17    49   -139us[ -117us] +/-   53ms

   You should only see your custom NTP sources.

Summary

This post demonstrated setting custom NTP servers on the AWS Transform discovery appliance.