NTP configuration with Elemental

Overview

The default OS channel shipped with Elemental provides NTP support via systemd-timesyncd.

This page covers configuring systemd-timesyncd with the provided SLE Micro images, which is pre-configured with some default (fallback) NTP servers: ([0-3].suse.pool.ntp.org).

The easiest way to configure a specific NTP server, is to drop a configuration file in the /etc/systemd/timesyncd.conf.d directory. The directory and the configuration file should be accessible by the systemd-timesync user.

Configure a static NTP server

The NTP configuration can be provided via a cloud-config snippet added to the MachineRegistration configuration.

We will need to:

  • ensure the timesyncd.conf.d directory can be read by the systemd-timesync user
  • write the custom config file in the timesyncd.conf.d directory
  • restart the systemd-timesyncd service to use the new configuration

As an example, let’s see how to configure ntp.ripe.net as the primary NTP server (lines 6-14):

  1. config:
  2.   cloud-config:
  3.     users:
  4.       - name: root
  5.         passwd: root
  6.     write_files:
  7.       - content: |
  8.           [Time]
  9.           NTP=ntp.ripe.net
  10.         path: /etc/systemd/timesyncd.conf.d/custom-ntp.conf
  11.         permissions: 644
  12.     runcmd:
  13.       - chmod 755 /etc/systemd/timesyncd.conf.d
  14.       - systemctl restart systemd-timesyncd
  15.   elemental:
  16.     install:
  17.       device: /dev/vda
  18.       reboot: true
  19. machineInventoryLabels:
  20.   element: fire

Configure NTP from DHCP

In order to get the NTP server from the network via the NTP DHCP option, we need a NetworkManager dispatcher script to reconfigure dynamically the systemd-timesync service when needed.

We will have both to:

  • provide the dispatcher script which creates and deletes the systemd-timesyncd config files
  • enable the NetworkManager-dispatcher service

See lines 6-34 in the following MachineRegistration configuration example:

  1. config:
  2.   cloud-config:
  3.     users:
  4.       - name: root
  5.         passwd: root
  6.     write_files:
  7.       - content: |
  8.           #! /usr/bin/bash
  10.           [ -n "$CONNECTION_UUID" ] || exit
  12.           INTERFACE=$1
  13.           ACTION=$2
  15.           case $ACTION in
  16.               up | dhcp4-change | dhcp6-change)
  17.                   [ -n "$DHCP4_NTP_SERVERS" ] || exit
  18.                   mkdir -p /etc/systemd/timesyncd.conf.d/
  19.                   cat<<EOF > /etc/systemd/timesyncd.conf.d/$CONNECTION_UUID.conf
  20.           [Time]
  21.           NTP=$DHCP4_NTP_SERVERS
  22.           RootDistanceMaxSec=15
  23.           EOF
  24.                   systemctl restart systemd-timesyncd
  25.                   ;;
  26.               down)
  27.                   rm -f /etc/systemd/timesyncd.conf.d/$CONNECTION_UUID.conf
  28.                   systemctl restart systemd-timesyncd
  29.                   ;;
  30.           esac
  31.         path: /etc/NetworkManager/dispatcher.d/10-update-timesyncd
  32.         permissions: 700
  33.     runcmd:
  34.       - systemctl enable NetworkManager-dispatcher
  35.   elemental:
  36.     install:
  37.       device: /dev/vda
  38.       reboot: true
  39. machineInventoryLabels:
  40.   element: fire