Setup AWS Timesync with the PTP clock for Ubuntu (x86 and arm tested)

aws-timesync-ptp.sh

#!/usr/bin/env bash
set -euo pipefail

echo "[1/6] Install build deps…"
sudo apt-get update -qq
sudo apt-get install -y --no-install-recommends \
        build-essential git linux-headers-$(uname -r)

echo "[2/6] Fetch & compile ENA with PHC…"
workdir=$(mktemp -d)
git -C "$workdir" clone --depth 1 https://github.com/amzn/amzn-drivers.git
cd "$workdir"/amzn-drivers/kernel/linux/ena
ENA_PHC_INCLUDE=1 make -j"$(nproc)"          # pulls in PHC support

echo "[3/6] Install the new module…"
sudo mkdir -p /lib/modules/$(uname -r)/updates
sudo cp -f ena.ko /lib/modules/$(uname -r)/updates/
sudo depmod -a

echo "[4/6] Enable PHC on load…"
echo "options ena phc_enable=1" | sudo tee /etc/modprobe.d/ena-phc.conf

echo "[5/6] Re-generate initramfs…"
sudo update-initramfs -u -k $(uname -r)

echo "[6/6] Done – rebooting to activate PHC-enabled ENA."
sleep 5
sudo reboot

then

cat /sys/module/ena/parameters/phc_enable   # should print “1”
ls /dev/ptp*                                # expect /dev/ptp0

And a one-liner to grab a bounded-error timestamp from the ptp clock:

First, configure chronyd to use the ptp clock:

echo 'refclock PHC /dev/ptp0 poll 0 prefer' | sudo tee /etc/chrony/conf.d/phc.conf
sudo systemctl restart chronyd

Then grab a time with:

printf '%s ±%.9f s\n'  \
  "$(date +%s.%N)"     \
  $(chronyc tracking -n | awk '
      /Last[ ]offset/      {off=$(NF-1)}
      /Root[ ]delay/       {rd =$(NF-1)/2}
      /Root[ ]dispersion/  {rp =$(NF-1)}
      END {
          if(off=="") off=0; if(rd=="") rd=0; if(rp=="") rp=0;
          if(off<0) off=-off;
          printf "%.9f", off+rd+rp   # root-distance formula
      }')

You'll see something like:

1751514577.054060088 ±0.000002144 s

that's 2.144 microseconds!!!

This will survive reboots as well

clockbound should automatically use the ptp clock once you tell chronyd to use the PHC (ptp hardware clock)