| chrony | |
|---|---|
 Screenshot of chronyc | |
| Original author | Richard Curnow[1] |
| Developers | Miroslav Lichvar,Red Hat[1] |
| Stable release | |
| Repository | |
| Written in | C |
| Operating system | Unix-like |
| Type | Time synchronization |
| License | GNU GPL v2 |
| Website | chrony-project |
chrony is an implementation of theNetwork Time Protocol (NTP). It is an alternative tontpd, areference implementation of NTP. It runs onUnix-likeoperating systems (includingLinux andmacOS) and is released under theGNU GPL v2.[3] It is the default NTPclient andserver inRed Hat Enterprise Linux 8 andSUSE Linux Enterprise Server 15,[4][5] and available in manyLinux distributions.[6][7][8]
Support for Network Time Security (NTS) was added in version 4.0.[9]
In contrast toNTPsec, which is a security-focused fork ofntpd, chrony was implemented from scratch.[1] It was designed to synchronize time even in difficult conditions such as intermittent network connections (such aslaptops) and congested networks.[1] 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.[10]
Unlikentpd, 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 aLAN[3] – to the order of 70 nanoseconds (from asymmetry),[11] comparable toPrecision Time Protocol. It also supports synchronization by manual input, so as to perform time correction within an isolated network.[3]
chrony does not implement broadcast,multicast, andanycast modes of operation. It also does not implement the insecure "autokey" authentication.[3] It uses external programs to drive hardware time sources (e.g.gpsd for GNSS), unlikentpd, which has many built-in drivers.[10]
