chrony is an implementation of the
Network Time Protocol
The Network Time Protocol (NTP) is a networking protocol for clock synchronization between computer systems over packet-switched, variable- latency data networks. In operation since before 1985, NTP is one of the oldest Internet protocols in ...
(NTP). It's an alternative to
ntpd
The Network Time Protocol daemon (ntpd) is an operating system program that maintains the system time in synchronization with time servers using the Network Time Protocol (NTP).
Description
The ntpd program is an operating-system daemon that s ...
, which is a
reference implementation
In the software development process, a reference implementation (or, less frequently, sample implementation or model implementation) is a program that implements all requirements from a corresponding specification. The reference implementation o ...
of NTP. It runs on
Unix-like
A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-li ...
operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
s (including
Linux
Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, whi ...
and
macOS
macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and la ...
) and is released under the
GNU GPL v2.
It's the default NTP
client
Client(s) or The Client may refer to:
* Client (business)
* Client (computing), hardware or software that accesses a remote service on another computer
* Customer or client, a recipient of goods or services in return for monetary or other valuabl ...
and
server
Server may refer to:
Computing
*Server (computing), a computer program or a device that provides functionality for other programs or devices, called clients
Role
* Waiting staff, those who work at a restaurant or a bar attending customers and su ...
in
Red Hat Enterprise Linux
Red Hat Enterprise Linux (RHEL) is a commercial open-source Linux distribution developed by Red Hat for the commercial market. Red Hat Enterprise Linux is released in server versions for x86-64, Power ISA, ARM64, and IBM Z and a desktop ...
8 and
SUSE Linux Enterprise Server
SUSE Linux Enterprise (often abbreviated to SLE) is a Linux-based operating system developed by SUSE. It is available in two editions, suffixed with Server (SLES) for servers and mainframes, and Desktop (SLED) for workstations and desktop com ...
15, and available in many
Linux distributions
A Linux distribution (often abbreviated as distro) is an operating system made from a software collection that includes the Linux kernel and, often, a package management system. Linux users usually obtain their operating system by downloading one ...
.
Support for Network Time Security (NTS) was added on version 4.0.
Comparison with the reference implementation
In contrast to
NTPsec, which is a security-focused fork of ntpd, chrony was implemented from scratch.
It was designed to synchronize time even in difficult conditions such as intermittent network connections (such as
laptops
A laptop, laptop computer, or notebook computer is a small, portable personal computer (PC) with a screen and alphanumeric keyboard. Laptops typically have a clam shell form factor with the screen mounted on the inside of the upper li ...
) and congested networks.
Some improvements in this regard (compared to reference ntpd) include that it never steps (abruptly adjusts) time outside of startup, can correct for asymmetric network jitters, and can use larger clock rate adjustments on Linux to deal with a broken clock. It typically synchronizes faster and more accurately.
[
Unlike , it supports synchronizing the system clock via hardware timestamping (i.e. packet times on the network adapter), improving accuracy of time synchronization between machines on a ]LAN
Lan or LAN may also refer to:
Science and technology
* Local asymptotic normality, a fundamental property of regular models in statistics
* Longitude of the ascending node, one of the orbital elements used to specify the orbit of an object in spa ...
multicast
In computer networking, multicast is group communication where data transmission is addressed to a group of destination computers simultaneously. Multicast can be one-to-many or many-to-many distribution. Multicast should not be confused wi ...
, and manycast modes of operation. It also does not implement the insecure "autokey" authentication.
See also
* OpenNTPD
OpenNTPD (also known as OpenBSD NTP Daemon) is a Unix daemon implementing the Network Time Protocol to synchronize the local clock of a computer system with remote NTP servers. It is also able to act as an NTP server to NTP-compatible clients.
...
References
External links
* {{Official website
Network time-related software
Free software programmed in C
Software using the GPL license