# Ntp

Published articles for Ntp.

This is one page of public article previews, not the complete archive. Follow Next page to continue. Summaries are not the original full articles.

## A Backward NTP Clock Step Delayed a Python Scheduler's Measurements by Nine Days

DevFeed: [A Backward NTP Clock Step Delayed a Python Scheduler's Measurements by Nine Days](<https://devfeed.tech/articles/the-ntp-clock-jump-that-made-the-scheduler-skip-a-week-of-measurements-34099.md>)

Original publisher: [Read original article](<https://philipptheserver.com/posts/clock-jump-scheduler/>)

Author: Philipp Lehmann (philipp.lehmann@gruppe.ai)

Published: 2026-09-14T07:00:00Z

Content type: tutorial

Language: en

Sources: [Philipp Lehmann](<https://devfeed.tech/sources/philipp-lehmann.md>)

Topics: [Python](<https://devfeed.tech/topics/python.md>), [Linux](<https://devfeed.tech/topics/linux.md>), [systemd](<https://devfeed.tech/topics/systemd.md>), [Single Board Computer](<https://devfeed.tech/topics/single-board-computer.md>)

Tags: [embedded](<https://devfeed.tech/tags/embedded.md>), [linux](<https://devfeed.tech/tags/linux.md>), [ntp](<https://devfeed.tech/tags/ntp.md>), [python](<https://devfeed.tech/tags/python.md>), [reliability](<https://devfeed.tech/tags/reliability.md>), [scheduler](<https://devfeed.tech/tags/scheduler.md>), [single-board-computer](<https://devfeed.tech/tags/single-board-computer.md>), [systemd](<https://devfeed.tech/tags/systemd.md>), [time](<https://devfeed.tech/tags/time.md>), [wall-clock-time](<https://devfeed.tech/tags/wall-clock-time.md>)

### AI overview

A Python scheduler on an embedded Linux device silently stopped running after NTP corrected the system clock backward by about nine days. Because it used wall-clock time to measure elapsed time, the scheduler waited roughly nine days before running again. The article explains why a monotonic clock is the appropriate fix and mentions testing with an injected clock jump.

### Source excerpt

time.time() vs time.monotonic() in a Python scheduler: a backwards NTP step delayed runs by nine days. Monotonic durations and a jump-injecting test.

## Rebuilding a 1995 GPS Time Server so I don't get Telstra'd

DevFeed: [Rebuilding a 1995 GPS Time Server so I don't get Telstra'd](<https://devfeed.tech/articles/rebuilding-a-1995-gps-time-server-so-i-don-t-get-telstra-d-10484.md>)

Original publisher: [Read original article](<https://www.jeffgeerling.com/blog/2026/truetime-xl-gps-time-server-restomod/>)

Author: jeff@jeffgeerling.com (Jeff Geerling)

Published: 2026-09-04T14:00:00Z

Content type: article

Language: en

Sources: [Jeff Geerling](<https://devfeed.tech/sources/jeff-geerling.md>)

Topics: [Hardware](<https://devfeed.tech/topics/hardware.md>), [Server](<https://devfeed.tech/topics/server.md>), [configuration](<https://devfeed.tech/topics/configuration.md>), [Network](<https://devfeed.tech/topics/network.md>), [data](<https://devfeed.tech/topics/data.md>)

Tags: [australia](<https://devfeed.tech/tags/australia.md>), [data](<https://devfeed.tech/tags/data.md>), [daytime](<https://devfeed.tech/tags/daytime.md>), [gps](<https://devfeed.tech/tags/gps.md>), [hardware](<https://devfeed.tech/tags/hardware.md>), [network](<https://devfeed.tech/tags/network.md>), [ntp](<https://devfeed.tech/tags/ntp.md>), [raspberry-pi](<https://devfeed.tech/tags/raspberry-pi.md>), [raspberry-pi-5](<https://devfeed.tech/tags/raspberry-pi-5.md>), [server](<https://devfeed.tech/tags/server.md>), [symmetricom](<https://devfeed.tech/tags/symmetricom.md>), [time](<https://devfeed.tech/tags/time.md>), [truetime](<https://devfeed.tech/tags/truetime.md>), [usb](<https://devfeed.tech/tags/usb.md>)

### AI overview

The article documents the restoration of a 1995 TrueTime GPS time server using a Raspberry Pi 5 and GNSS HAT. It explains the hardware integration and configuration of the Pi as a stratum 1 NTP server, including Chrony, LCD and LED status displays, and timing protocols.

### Source excerpt

In June I purchased this TrueTime XL-AK time server, so I could learn more of the history of GPS-based time. I received it on June 22, and just 16 days later a similar GPS time server took down Australia's cell service for 12 hours! I made a short video about it but put off digging into the TrueTime... until now. Over the past couple weeks, I've 'restomodded' this device with a Raspberry Pi, to build a stratum 1 NTP Time server, which I'd like to eventually add to the NTP Pool. I found a way to drop in a Pi 5 and GNSS HAT, display the time and GPS status on the built-in 16x2 LCD, show the status on the bicolor LED, and make this box useful again.

## Before NTP there were Time and Daytime

DevFeed: [Before NTP there were Time and Daytime](<https://devfeed.tech/articles/before-ntp-there-were-time-and-daytime-10481.md>)

Original publisher: [Read original article](<https://www.jeffgeerling.com/blog/2026/rfc-867-868-time/>)

Author: jeff@jeffgeerling.com (Jeff Geerling)

Published: 2026-08-30T22:09:00Z

Content type: article

Language: en

Sources: [Jeff Geerling](<https://devfeed.tech/sources/jeff-geerling.md>)

Topics: [networking](<https://devfeed.tech/topics/networking.md>), [Protocol (disambiguation)](<https://devfeed.tech/topics/protocol.md>), [Unix](<https://devfeed.tech/topics/unix.md>)

Tags: [apple](<https://devfeed.tech/tags/apple.md>), [bug](<https://devfeed.tech/tags/bug.md>), [daytime](<https://devfeed.tech/tags/daytime.md>), [history](<https://devfeed.tech/tags/history.md>), [network](<https://devfeed.tech/tags/network.md>), [ntp](<https://devfeed.tech/tags/ntp.md>), [rfc-867](<https://devfeed.tech/tags/rfc-867.md>), [rfc-868](<https://devfeed.tech/tags/rfc-868.md>), [server](<https://devfeed.tech/tags/server.md>), [time](<https://devfeed.tech/tags/time.md>)

### AI overview

The article examines the pre-NTP Time and Daytime protocols, RFC 868 and RFC 867, and explains how they provided simple network-based time retrieval. It describes the protocols' low overhead and limitations, including one-second resolution, lack of network-delay measurement, and the 2036 32-bit rollover bug.

### Source excerpt

In building an NTP time demo on old Macs for VCF Midwest, I came across RFC 867 and RFC 868, for the 'Daytime' and 'Time' Protocols, respectively. My first exposure to any form of network time was when I upgraded from a used PowerBook 180c to my first 'new' computer, a Power Mac G3, in 2000. With the introduction of Mac OS 8.5, Apple added a 'Network Time Server' option in the Date & Time Control Panel.

## The lingering legacy of 'reserved' ports

DevFeed: [The lingering legacy of 'reserved' ports](<https://devfeed.tech/articles/the-lingering-legacy-of-reserved-ports-10853.md>)

Original publisher: [Read original article](<https://blog.apnic.net/2026/08/28/the-lingering-legacy-of-reserved-ports/>)

Author: George Michaelson

Published: 2026-08-27T23:29:48Z

Content type: article

Language: en

Sources: [APNIC Blog](<https://devfeed.tech/sources/apnic-blog.md>)

Topics: [Protocol (disambiguation)](<https://devfeed.tech/topics/protocol.md>), [Network](<https://devfeed.tech/topics/network.md>), [Process](<https://devfeed.tech/topics/process.md>), [Operating system](<https://devfeed.tech/topics/operating-system.md>), [Unix](<https://devfeed.tech/topics/unix.md>), [ssh](<https://devfeed.tech/topics/ssh.md>), [Firewall](<https://devfeed.tech/topics/firewall.md>), [Internet](<https://devfeed.tech/topics/internet.md>)

Tags: [dns](<https://devfeed.tech/tags/dns.md>), [firewall](<https://devfeed.tech/tags/firewall.md>), [history](<https://devfeed.tech/tags/history.md>), [internet](<https://devfeed.tech/tags/internet.md>), [network](<https://devfeed.tech/tags/network.md>), [ntp](<https://devfeed.tech/tags/ntp.md>), [opinion](<https://devfeed.tech/tags/opinion.md>), [process](<https://devfeed.tech/tags/process.md>), [processes](<https://devfeed.tech/tags/processes.md>), [ssh](<https://devfeed.tech/tags/ssh.md>), [systems](<https://devfeed.tech/tags/systems.md>), [tech-matters](<https://devfeed.tech/tags/tech-matters.md>)

### AI overview

An exploration of why reserved TCP and UDP ports persist, tracing conventions such as ports 22, 53, 80, and 443 to early Internet services on multi-user systems. It explains the relationship between ports, protocol-specific daemons, operating-system administration, and modern firewall and service-discovery practices.

### Source excerpt

Modern service discovery mechanisms increasingly allow services to run on arbitrary ports, yet DNS may remain the one protocol that cannot fully escape its dependency on the long-established convention of port 53.

## Behind the scenes: debugging a pool join failure

DevFeed: [Behind the scenes: debugging a pool join failure](<https://devfeed.tech/articles/behind-the-scenes-debugging-a-pool-join-failure-12821.md>)

Original publisher: [Read original article](<https://xcp-ng.org/blog/2026/07/20/behind-the-scenes-debugging-a-pool-join-failure/>)

Author: Marc Pezin

Published: 2026-07-20T09:48:38Z

Content type: article

Language: en

Sources: [XCP-ng Blog](<https://devfeed.tech/sources/xcp-ng-blog.md>)

Topics: [debugging](<https://devfeed.tech/topics/debugging.md>), [TLS (Transport Layer Security)](<https://devfeed.tech/topics/tls.md>), [DevOps](<https://devfeed.tech/topics/devops.md>), [Server](<https://devfeed.tech/topics/server.md>)

Tags: [analysis](<https://devfeed.tech/tags/analysis.md>), [contribution](<https://devfeed.tech/tags/contribution.md>), [debugging](<https://devfeed.tech/tags/debugging.md>), [devblog](<https://devfeed.tech/tags/devblog.md>), [error-reporting](<https://devfeed.tech/tags/error-reporting.md>), [ntp](<https://devfeed.tech/tags/ntp.md>), [root-cause-analysis](<https://devfeed.tech/tags/root-cause-analysis.md>), [tls](<https://devfeed.tech/tags/tls.md>)

### AI overview

This article follows the investigation of an XCP-ng pool join failure after an upgrade from version 8.2 to 8.3. The debugging process reproduced the issue, ruled out common TLS causes, identified the root cause, and resulted in an upstream contribution that improved error reporting.

### Source excerpt

A user reported a pool join failure after upgrading to XCP-ng 8.3. What started as a forum discussion led to a root-cause analysis, an upstream contribution, and a better error message for everyone.

## How clock drift and network latency affect distributed database writes, and how Spanner uses TrueTime

DevFeed: [How clock drift and network latency affect distributed database writes, and how Spanner uses TrueTime](<https://devfeed.tech/articles/clock-synchronization-is-a-nightmare-why-spanner-uses-truetime-and-the-rest-of-us-suffer-39579.md>)

Original publisher: [Read original article](<https://ankit-rana.com/logs/27-clock-synchronization-truetime/>)

Author: hello@ankit-rana.com

Published: 2026-05-17T00:00:00Z

Content type: article

Language: en

Sources: [Ankit Rana | Mechanical Sympathy](<https://devfeed.tech/sources/ankit-rana-mechanical-sympathy.md>)

Topics: [distributed-systems](<https://devfeed.tech/topics/distributed-systems.md>), [Databases](<https://devfeed.tech/topics/databases.md>), [Network](<https://devfeed.tech/topics/network.md>), [Latency](<https://devfeed.tech/topics/latency.md>), [Hardware](<https://devfeed.tech/topics/hardware.md>), [Google](<https://devfeed.tech/topics/google.md>)

Tags: [clocks](<https://devfeed.tech/tags/clocks.md>), [consistency](<https://devfeed.tech/tags/consistency.md>), [data](<https://devfeed.tech/tags/data.md>), [databases](<https://devfeed.tech/tags/databases.md>), [distributed-systems](<https://devfeed.tech/tags/distributed-systems.md>), [google](<https://devfeed.tech/tags/google.md>), [gps](<https://devfeed.tech/tags/gps.md>), [hardware](<https://devfeed.tech/tags/hardware.md>), [latency](<https://devfeed.tech/tags/latency.md>), [network](<https://devfeed.tech/tags/network.md>), [ntp](<https://devfeed.tech/tags/ntp.md>), [spanner](<https://devfeed.tech/tags/spanner.md>), [synchronization](<https://devfeed.tech/tags/synchronization.md>), [truetime](<https://devfeed.tech/tags/truetime.md>)

### AI overview

The article explains how quartz-clock drift and variable network latency limit NTP synchronization across servers. It describes how clock skew can cause last-write-wins conflict resolution to silently discard a newer database write, and presents Google Spanner's use of GPS, atomic clocks, and TrueTime uncertainty intervals as a mitigation.

### Source excerpt

Server clocks come from quartz crystals that drift with temperature, and NTP cannot fully correct them because you cannot measure absolute time over a variable-latency network. Under last-write-wins, a node whose clock runs 10 ms fast can silently discard a newer write from a node that is behind: no error, normal logs, lost user data. Spanner solves it with GPS and atomic clocks, where TrueTime returns an uncertainty interval and the commit waits it out.

## SPI Flash for Persistent Data Storage with NuttX RTOS

DevFeed: [SPI Flash for Persistent Data Storage with NuttX RTOS](<https://devfeed.tech/articles/spi-flash-for-persistent-data-storage-with-nuttx-rtos-13725.md>)

Original publisher: [Read original article](<https://developer.espressif.com/blog/2025/09/nuttx-storing-data-spi-flash/>)

Author: John Lee

Published: 2025-09-23T00:00:00Z

Content type: tutorial

Language: en

Sources: [Blog on Developer Portal](<https://devfeed.tech/sources/blog-on-developer-portal.md>)

Topics: [NuttX](<https://devfeed.tech/topics/nuttx.md>), [Embedded Systems](<https://devfeed.tech/topics/embedded-systems.md>), [Filesystems](<https://devfeed.tech/topics/filesystems.md>), [data-processing](<https://devfeed.tech/topics/data-processing.md>), [Logging](<https://devfeed.tech/topics/logging.md>), [Espressif](<https://devfeed.tech/topics/espressif.md>), [boot](<https://devfeed.tech/topics/boot.md>)

Tags: [apache](<https://devfeed.tech/tags/apache.md>), [applications](<https://devfeed.tech/tags/applications.md>), [blog](<https://devfeed.tech/tags/blog.md>), [boot](<https://devfeed.tech/tags/boot.md>), [code](<https://devfeed.tech/tags/code.md>), [configuration](<https://devfeed.tech/tags/configuration.md>), [data](<https://devfeed.tech/tags/data.md>), [developers](<https://devfeed.tech/tags/developers.md>), [embedded](<https://devfeed.tech/tags/embedded.md>), [esp32](<https://devfeed.tech/tags/esp32.md>), [espressif](<https://devfeed.tech/tags/espressif.md>), [examples](<https://devfeed.tech/tags/examples.md>), [firmware](<https://devfeed.tech/tags/firmware.md>), [flash](<https://devfeed.tech/tags/flash.md>), [guide](<https://devfeed.tech/tags/guide.md>), [how-to](<https://devfeed.tech/tags/how-to.md>), [implementation](<https://devfeed.tech/tags/implementation.md>), [logging](<https://devfeed.tech/tags/logging.md>), [memory](<https://devfeed.tech/tags/memory.md>), [ntp](<https://devfeed.tech/tags/ntp.md>), [nuttx](<https://devfeed.tech/tags/nuttx.md>), [spi](<https://devfeed.tech/tags/spi.md>), [spiffs](<https://devfeed.tech/tags/spiffs.md>), [storage](<https://devfeed.tech/tags/storage.md>), [systems](<https://devfeed.tech/tags/systems.md>)

### AI overview

This guide explains how to use Espressif device flash memory for persistent data storage with NuttX. It covers SPI Flash NOR fundamentals, compares file systems including SmartFS, SPIFFS, and LittleFS, and demonstrates a Wi-Fi application that synchronizes the system clock and logs the current time to a flash-resident file.

### Source excerpt

This guide explores how to utilize flash memory for persistent data storage in NuttX-based embedded systems, covering SPI Flash fundamentals, file system options (SmartFS, SPIFFS, LittleFS), and practical implementation of a boot time logging application with Wi-Fi and NTP synchronization.

## What time is it? A simple question with a complex answer. How computers synchronize time

DevFeed: [What time is it? A simple question with a complex answer. How computers synchronize time](<https://devfeed.tech/articles/what-time-is-it-a-simple-question-with-a-complex-answer-how-computers-synchronize-time-27113.md>)

Original publisher: [Read original article](<https://andrea.corbellini.name/2023/01/23/what-time-is-it/>)

Author: andreacorbellini

Published: 2023-01-23T19:15:00Z

Content type: article

Language: en

Sources: [Andrea Corbellini](<https://devfeed.tech/sources/andrea-corbellini.md>)

Topics: [DateTime](<https://devfeed.tech/topics/datetime.md>), [Network](<https://devfeed.tech/topics/network.md>), [Protocol (disambiguation)](<https://devfeed.tech/topics/protocol.md>)

Tags: [clocks](<https://devfeed.tech/tags/clocks.md>), [information-technology](<https://devfeed.tech/tags/information-technology.md>), [network](<https://devfeed.tech/tags/network.md>), [ntp](<https://devfeed.tech/tags/ntp.md>), [performance](<https://devfeed.tech/tags/performance.md>), [protocol](<https://devfeed.tech/tags/protocol.md>), [ptp](<https://devfeed.tech/tags/ptp.md>), [relativity](<https://devfeed.tech/tags/relativity.md>), [standard](<https://devfeed.tech/tags/standard.md>), [time](<https://devfeed.tech/tags/time.md>), [time-synchronization](<https://devfeed.tech/tags/time-synchronization.md>)

### AI overview

This article explains why accurate time synchronization matters for computers, phones, applications, and other devices. It introduces challenges in synchronizing time and examines the Network Time Protocol (NTP) and Precision Time Protocol (PTP), while also discussing concepts including time, change, causality, and the definition of a second.

### Source excerpt

Ever wondered how your computer or your phone displays the current date and time accurately? What keeps all the devices in the world (and in space) in agreement on what time it is? What makes applications that require precise timing possible? In this article, I will explain some of the challenges with time synchronization and explore two of the most popular protocols that devices ...