Elastic Compute Service:Enable PTP clock synchronization for ECS instances

Service access

Invitational preview — The PTP time synchronization feature is currently in invitational preview. To use this feature, submit a ticket to apply.

Instance resources

Regions and zones

PTP is supported in the following regions and zones:

Instance families

PTP is supported by the following instance families:

• general-purpose instance family g9i, compute-optimized instance family c9i, and memory-optimized instance family r9i (invitational preview)

• General-purpose ECS Bare Metal instance families ebmg9i, ebmc9i, and ebmr9i (invitational preview)

• High-clock speed compute-optimized instance family hfc9i, high-clock speed general-purpose instance family hfg9i, and high-clock speed memory-optimized instance family hfr9i

  To check whether a specific instance type supports PTP, call the DescribeInstanceTypes operation. If the PtpSupport parameter in the Clock parameter of the response is set to supported, the instance type supports PTP. If the instance type does not support PTP, the PtpSupport parameter is not included in the response.

Images

Linux images are supported. (Recommended) Use a maintained official image version. The following table lists the supported operating system versions.

Kernel version

The Linux kernel version must be 4.12 or later.

In-instance environment

• Cloud Assistant — The public command method and the plugin method require Cloud Assistant, which is pre-installed on public images. If Cloud Assistant is not installed, see install the Cloud Assistant Agent.

• Internet access — The installation package method downloads the ptp-monitor script package over the internet. Make sure that the instance can access the internet.

Step 2: Create or add ECS instances in the deployment set

All ECS instances in a deployment set are deployed within the same network topology scope (PSW) in the same zone, which reduces network latency. The instances are also distributed across different physical servers as much as possible to reduce the business impact of a single-server failure.

Create ECS instances with the PTP time synchronization service enabled in the deployment set, or enable the PTP time synchronization service for existing ECS instances and add them to the deployment set:

Step 3: Configure PTP for the instances in the deployment set

Install the PTP driver on each instance in the deployment set and configure the PTP clock in chrony. For instructions, see Enable the PTP time synchronization service.

Stage 1: Enable PTP for the instance in the ECS console

Stage 2: Install the PTP driver and configure chrony in the instance

1. Remotely connect to the Linux instance.

2. Choose a configuration method and complete the steps in the corresponding tab.

   Public commands and plugin features require Cloud Assistant. The following table describes when to use each method:

bash ptp-monitor.sh --start

View the PTP synchronization status

Run chronyc sources to view the status of the configured time sources (PTP and NTP). PTP synchronization is working when the PHC0 source is marked with #*.

Sample output:

The following example shows an instance that has the PTP time synchronization service enabled and configured. The instance uses the PTP hardware clock as its primary synchronization source, and the measured offset is at the nanosecond level:

[root@iZxxx Z ptp-monitor-latest]# chronyc sources
MS Name/IP address         Stratum Poll Reach LastRx Last sample
===============================================================================
#* PHC0                          0   4    56    37   -28ns[  -13ns] +/-   320ns

• MS: the time source identifier. PHC0 indicates the PTP hardware clock. An IP address indicates an NTP server. #* marks the current synchronization source, which means that the instance is using the PTP hardware clock.

• Stratum: the stratum of the time source. A lower value indicates higher accuracy (0 is an atomic clock or GPS, and 1 is a directly connected high-precision source).

• Poll: the polling interval exponent. The current polling interval is 2^Poll seconds. For example, Poll=4 indicates 16 seconds.

• Reach: an octal value that indicates the success rate of the last eight synchronization attempts.

• LastRx: the time since the last response was received, in seconds.

• Last sample: the clock offset from the last measurement, in the format offset [raw offset] +/- error, which reflects the difference between the system time and the source time.

Monitor PTP synchronization health

Run chronyc tracking to monitor and evaluate the health of the system clock, including dynamic metrics such as time bias, frequency error, and network latency, to ensure reliability for time-sensitive applications such as financial trading.

Sample output:

In the following example, the measured time bias is at the nanosecond level (System time = 1 ns, RMS offset = 1,175 ns), which meets high-precision requirements, and the frequency error is low (5.213 ppm), which indicates stable hardware clock operation:

[root@iZ*** ptp-monitor-latest]# chronyc tracking
Reference ID  : 50484330 (PHC0)
Stratum       : 1
Ref time (UTC) : Fri Aug 08 02:52:40 2025
System time   : 0.000000001 seconds fast of NTP time
Last offset   : -0.000000973 seconds
RMS offset    : 0.000001175 seconds
Frequency     : 5.213 ppm slow
Residual freq : -0.001 ppm
Skew          : 0.031 ppm
Root delay    : 0.000000001 seconds
Root dispersion : 0.000038351 seconds
Update interval : 16.0 seconds
Leap status   : Normal

• System time: the current bias between the system clock and the PTP hardware clock PHC0. slow means that the system time is 1 nanosecond behind (1 ns = 10⁻⁹ s).

• RMS offset: the long-term root mean square offset, which is 1,175 nanoseconds in this example and reflects synchronization stability.

• Frequency: the frequency bias of the system clock. slow means that the local clock runs 5.213 microseconds per second slower than the PTP hardware clock PHC0 (ppm = parts per million).

• Root delay: the total network latency to the root time source. The very low latency in the figure indicates a highly stable network environment.

Stage 1: Disable PTP for the instance in the ECS console

1. Go to and click the ID of the target instance to go to the instance details page.

2. On the Instance Details page, choose All Operations > Instance Settings > Configure PTP Clock Synchronization Service.

3. In the Configure PTP Clock Synchronization Service dialog box, disable the PTP time synchronization service and click OK. The PTP Time Synchronization Task window appears.

4. Click the task ID to view the task progress. After the task is complete, the dialog box closes automatically and PTP is disabled for the instance.

Stage 2: Remove the PTP clock source in the instance

Disabling PTP removes the PTP device. This updates the chrony configuration file to remove the PTP hardware clock source, restarts the chronyd service to restore default clock services such as NTP, and stops the ptp-monitor program.

1. Remotely connect to the Linux instance.

2. Choose a method and complete the steps in the corresponding tab.

   Public commands and plugin features require Cloud Assistant. Cloud Assistant is pre-installed on public images. For an instance that does not use a public image, use the installation package.

acs-plugin-manager --exec --plugin ACS-PTP-Monitor --params --stop

bash ptp-monitor.sh --stop

Confirm that PTP is disabled

Run chronyc sources to confirm that the PHC0 source is no longer listed and that the instance synchronizes with an NTP server. For instructions, see View the PTP synchronization status.

To use PTP on the instance again, repeat the procedure in Enable the PTP time synchronization service. To remove the PTP driver from the instance, see How do I uninstall the PTP driver?.

Can I enable or disable the PTP time synchronization service by using OpenAPI?

Yes. Use the instance creation operation for new instances and the clock options operation for existing instances, and then run the in-instance configuration commands remotely.

• Create an instance: call the RunInstances operation and set PtpStatus in ClockOptions to enabled or disabled to create an ECS instance with the PTP time synchronization service enabled or disabled.

• For an existing instance: call the ModifyInstanceClockOptions operation and set PtpStatus to enabled or disabled to enable or disable the PTP time synchronization service for the instance.

  On success, a task ID (TaskId) is returned. You can call the DescribeTasks operation with TaskAction set to ModifyInstanceClockOptions and TaskIds set to the corresponding task ID to query the execution status of the enable or disable operation in real time.

• Check the result: call the DescribeInstances operation with AdditionalAttributes set to CLOCK_OPTIONS to confirm whether the PTP time synchronization service is enabled for the instance.

• Configure the instance: call the RunCommand operation to run the relevant commands and complete the configuration.

Can PTP be used with NTP?

Yes. PTP does not affect NTP. chronyd uses an internal algorithm to select the best clock source and prioritizes PTP based on the configuration.

Why does the "dkms: command not found" error occur when I install the driver?

Installing the PTP driver first installs the required tool packages, and dkms is one of them, so you must resolve the dkms package installation issue. For detailed error logs about the driver installation failure, see /var/log/ptp-cipu-ptp-monitor.log.

• Scenario 1: the repo source configuration may not be up to date. Update the repo source and try again.

• Scenario 2: get the corresponding installation package from the official dkms website.

How do I enable or disable auto-start for the ptp-monitor program?

ptp-monitor is an O&M component that runs inside the instance. Keeping it running is recommended but not mandatory. After installation, the component starts automatically on boot by default.

• Disable auto-start on boot.

acs-plugin-manager --exec --plugin ACS-PTP-Monitor --params --disable-service

• Enable auto-start on boot.

acs-plugin-manager --exec --plugin ACS-PTP-Monitor --params --enable-service

How do I uninstall the PTP driver?

The PTP driver is named ptp_cipu. The driver is required for the PTP feature, and installing it does not affect the instance. To uninstall the PTP driver, run the following Cloud Assistant command:

acs-plugin-manager --exec --plugin ACS-PTP-Monitor --params --uninstall