Configuring Chrony NTP Sync for xCAT Compute Nodes

Lab environment: labtesting (xCAT Management Node) — Rocky Linux 8.10

1. Overview

This document describes the procedure used to configure chrony (NTP) time synchronization on xCAT-managed compute nodes.

The compute node is configured to synchronize its system clock against the xCAT Management Node (MN) rather than an external time source.

The configuration is delivered through a custom xCAT postscript, assigned to the target node, and pushed using updatenode.

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2. Environment Details

Item	Value
Management Node	labtesting (192.168.245.128)
Compute Node	cnode01
Operating System	Rocky Linux 8.10
Provisioning Tool	xCAT
Time Service	chronyd
Timezone	Asia/Kolkata (IST, +0530)

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3. Procedure

3.1 Verify chronyd State on the Management Node

Before making changes, confirm that chronyd is running on the management node and check its current time sources and connected clients.

chronyc sources
chronyc clients

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3.2 Create the xCAT Postscript

Create a custom postscript named setup_chrony_client under:

/install/postscripts/

The postscript:

1. Resolves the management node IP using the xCAT $MASTER variable.
2. Creates /etc/chrony.conf.
3. Configures the management node as the NTP server.
4. Enables and restarts chronyd.
5. Displays a confirmation message.

Create the postscript:

vi /install/postscripts/setup_chrony_client

Add the following content:

#!/bin/bash

# Configures this node's chronyd to sync against the xCAT
# management node

MASTER_IP=$(getent hosts $MASTER | awk '{print $1}')

cat > /etc/chrony.conf << CHRONY
server ${MASTER_IP} iburst
driftfile /var/lib/chrony/drift
makestep 1.0 3
rtcsync
logdir /var/log/chrony
CHRONY

systemctl enable --now chronyd
systemctl restart chronyd

echo "chrony client configured against master ${MASTER_IP}"

Make the postscript executable:

chmod +x /install/postscripts/setup_chrony_client

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3.3 Assign the Postscript to the Target Node

Add the postscript to the node definition:

chdef cnode01 -p postscripts=setup_chrony_client

Confirm that the postscript has been added:

lsdef cnode01 -i postscripts

Expected output:

Object name: cnode01
 postscripts=syslog,remoteshell,syncfiles,setup_chrony_client

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3.4 Push the Postscript to the Node

Run the postscript on the live compute node using updatenode:

updatenode cnode01 -P setup_chrony_client

Expected output:

cnode01: postscript start..: setup_chrony_client
cnode01: chrony client configured against master 192.168.245.128
cnode01: postscript end....: setup_chrony_client exited with code 0

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4. Verification

4.1 Verify the Compute Node's NTP Source

From the management node, check the chrony sources on cnode01:

xdsh cnode01 chronyc sources

The management node should appear as the selected (*) time source.

Example:

cnode01: ^* labtesting.local.com.lab> 10 6 17 54 +42us[ +299us] +/- 463us

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4.2 Verify the Node is Registered as a Chrony Client

On the management node:

chronyc clients

Example:

Hostname  NTP  Drop  Int  IntL  Last  Cmd  Drop  Int  Last
cnode01   13   0     6    -     47    0    0     -    -

The presence of cnode01 confirms that the compute node is actively polling the management node.

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4.3 Verify System Clock Synchronization

On the compute node, verify the system time synchronization state:

xdsh cnode01 timedatectl

Expected output:

cnode01: System clock synchronized: yes
cnode01: NTP service: active
cnode01: Time zone: Asia/Kolkata (IST, +0530)

The verification confirms that the system clock is synchronized and the NTP service is active.

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5. Result

The configuration was successfully completed for compute node cnode01.

• cnode01 successfully synchronizes its clock with the xCAT management node labtesting (192.168.245.128) using chrony.
• chronyc sources on cnode01 shows the management node as the selected (*) time source.
• chronyc clients on the management node shows cnode01 actively polling.
• timedatectl on cnode01 confirms:
• System clock synchronized: yes
• NTP service: active
• Timezone: Asia/Kolkata (IST, +0530)

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6. Notes / Follow-ups

Apply the Configuration to Additional Nodes

The postscript uses xCAT's $MASTER variable, so it can automatically resolve the correct management node IP when applied to another node.

For a node range or group:

chdef <noderange> -p postscripts=setup_chrony_client

Then push the postscript:

updatenode <noderange> -P setup_chrony_client

Automatically Configure Newly Provisioned Nodes

For newly provisioned nodes, consider adding setup_chrony_client to the default postscript list of the relevant xCAT osimage.

This allows new compute nodes to automatically receive the chrony client configuration during provisioning.

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7. Quick Command Reference

Purpose	Command
Check NTP sources	chronyc sources
Check NTP clients	chronyc clients
Create postscript	vi /install/postscripts/setup_chrony_client
Make postscript executable	chmod +x /install/postscripts/setup_chrony_client
Assign postscript	chdef cnode01 -p postscripts=setup_chrony_client
Verify postscript assignment	lsdef cnode01 -i postscripts
Push postscript	updatenode cnode01 -P setup_chrony_client
Check node chrony source	xdsh cnode01 chronyc sources
Check node time status	xdsh cnode01 timedatectl

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8. Architecture

                 NTP / Time Source
                        |
                        v
              +---------------------+
              | xCAT Management Node |
              |     labtesting       |
              |   192.168.245.128    |
              |       chronyd        |
              +----------+----------+
                         |
                  xCAT / Network
                         |
                         v
              +---------------------+
              |   Compute Node       |
              |      cnode01         |
              |       chronyd        |
              +---------------------+
                         |
                         v
                 System Clock Sync

Flow:

xCAT Management Node → chronyd → cnode01 chronyd → synchronized system clock