ntpd-rs is a modern NTP implementation written in Rust by Trifecta Tech Foundation (with NLnet/ISRG funding). It supports NTS, has memory safety guarantees from Rust, and aims to be a secure, modern alternative. It reached v1.0 in 2024 and is suitable for production use.

Chrony vs ntpd vs systemd-timesyncd | NTP Client Comparison 2026

Q: Should I use chrony or ntpd?

Use chrony. It's the recommended NTP client for all modern Linux distributions. It converges faster, handles intermittent connectivity better, supports NTS (Network Time Security), and has lower resource usage. ntpd is considered legacy and no longer receives major updates.

Q: What is the difference between chrony and systemd-timesyncd?

systemd-timesyncd is a lightweight SNTP client suitable for desktops and containers that only need basic time sync. chrony is a full NTP implementation that can act as both client and server, supports NTS, handles hardware reference clocks, and provides sub-millisecond accuracy. Use chrony for servers and infrastructure, timesyncd for minimal setups.

Q: Does ntpd support NTS (Network Time Security)?

No. The reference ntpd implementation does not support NTS. Only chrony (v4.0+), NTPsec, and ntpd-rs support NTS. If you need authenticated time synchronization, you must switch to one of these alternatives.

TL;DR — Quick Recommendation

Use Case	Recommendation	Why
Production servers	chrony	Full NTP + NTS, fast convergence, server mode
Desktop Linux	chrony or timesyncd	chrony for best accuracy, timesyncd if already installed
Containers / minimal VMs	timesyncd	Smallest footprint, no config needed
Security-critical	chrony + NTS	Only mature NTS implementation
NTP server / pool	chrony	Can serve time, handle hardware refclocks
Memory-safe alternative	ntpd-rs	Rust-based, NTS support, production-ready since 2024

Feature Comparison Table

Feature	chrony	ntpd (ref)	timesyncd	ntpd-rs
NTP client	Yes	Yes	Yes (SNTP)	Yes
NTP server	Yes	Yes	No	Yes
NTS support	Yes (v4.0+)	No	No	Yes
Hardware refclocks	Yes (PPS, SHM, SOCK)	Yes	No	No
Leap smearing	Yes	Limited	No	Yes
Fast initial sync	Seconds	Minutes	Seconds	Seconds
Intermittent network	Excellent	Poor	OK	Good
Memory safety	C (audited)	C (legacy)	C (systemd)	Rust
Monitoring CLI	`chronyc`	`ntpq`	`timedatectl`	`ntp-ctl`
Active development	Yes	Minimal	Yes	Yes
Default on	RHEL, Fedora, CentOS, Arch	Legacy systems	Ubuntu, Debian	—

Chrony: The Modern Standard

Chrony is the recommended NTP client for virtually all modern Linux deployments. Written by Miroslav Lichvar (Red Hat), it was designed from the ground up to handle real-world conditions that ntpd struggles with.

Key Advantages

Fast convergence — Syncs within seconds of startup, vs minutes for ntpd
NTS support — Cryptographic authentication via TLS 1.3 (since v4.0)
Intermittent connectivity — Handles laptops, mobile devices, and unstable networks gracefully
VM-friendly — Handles clock jumps from live migration and snapshot restore
Lower resource usage — Less CPU and memory than ntpd

Minimal Configuration

# /etc/chrony/chrony.conf server ntp-pool.rdem-systems.com iburst nts server ptbtime1.ptb.de iburst nts server time.cloudflare.com iburst nts pool pool.ntp.org iburst driftfile /var/lib/chrony/drift makestep 1.0 3 rtcsync

Essential Commands

root@server:~# chronyc tracking # Overall sync status root@server:~# chronyc sources -v # List time sources root@server:~# chronyc authdata # NTS authentication status root@server:~# chronyc makestep # Force immediate correction

ntpd: The Legacy Reference

The original NTP daemon, developed by David L. Mills starting in 1985. While historically important, it is now considered legacy software.

Still Using ntpd? Check Your Sync

root@server:~# ntpq -p remote refid st t when poll reach delay offset jitter ============================================================================== *pool-ntp.rdem-s .GPS. 1 u 34 64 377 4.231 0.145 0.089

systemd-timesyncd: The Lightweight Option

Built into systemd, systemd-timesyncd is a minimal SNTP client. It handles basic time synchronization with almost zero configuration.

When It's Enough

Desktop systems that just need "correct enough" time
Containers where minimal footprint matters
Systems where installing additional packages is undesirable

When It's Not Enough

You need to serve time to other machines
You need NTS (authenticated time)
You need sub-millisecond accuracy
You need hardware reference clock support

Configuration

# /etc/systemd/timesyncd.conf [Time] NTP=ntp-pool.rdem-systems.com pool.ntp.org FallbackNTP=time.cloudflare.com

root@server:~# timedatectl status Local time: Mon 2026-03-10 14:30:15 CET Universal time: Mon 2026-03-10 13:30:15 UTC RTC time: Mon 2026-03-10 13:30:15 Time zone: Europe/Paris (CET, +0100) System clock synchronized: yes NTP service: active

ntpd-rs: The Rust Newcomer

ntpd-rs is a modern NTP implementation written in Rust by the Trifecta Tech Foundation, funded by NLnet and ISRG (the organization behind Let's Encrypt). It reached v1.0 in 2024.

Key Features

Memory safety — Rust eliminates entire categories of security vulnerabilities
NTS support — Built-in from the start
Modern architecture — Async I/O, structured logging
NTP server mode — Can serve time to clients

Installation

# From source (requires Rust toolchain) $ cargo install ntpd-rs # Or via package manager (where available) root@server:~# apt install ntpd-rs # future packaging

Migrating from ntpd to chrony

Step 1: Note your current servers

root@server:~# grep "^server\|^pool" /etc/ntp.conf server 0.pool.ntp.org iburst server 1.pool.ntp.org iburst

Step 2: Install chrony and remove ntpd

# Debian/Ubuntu root@server:~# apt install chrony && apt remove ntp # RHEL/CentOS root@server:~# dnf install chrony && dnf remove ntp

Step 3: Configure chrony

# /etc/chrony/chrony.conf # Use your existing servers + add NTS server ntp-pool.rdem-systems.com iburst nts pool pool.ntp.org iburst driftfile /var/lib/chrony/drift makestep 1.0 3 rtcsync # If acting as NTP server for your LAN: allow 192.168.0.0/16 allow 10.0.0.0/8

Step 4: Start and verify

root@server:~# systemctl enable --now chronyd root@server:~# chronyc sources -v .-- Source mode '^' = server, '=' = peer, '#' = local clock. / .- Source state '*' = current best, '+' = combined, '-' = not combined, | / 'x' = may be in error, '~' = too variable, '?' = unusable. || .- xxxx [ yyyy ] +/- zzzz || Ref ID Stratum Poll Reach LastRx Last sample =============================================================================== ^* ntp-pool.rdem> 2 6 377 23 -145us[ -201us] +/- 12ms

Frequently Asked Questions

Should I use chrony or ntpd?

Use chrony. It converges faster, handles intermittent connectivity better, supports NTS, and uses fewer resources. ntpd is legacy software.

What is the difference between chrony and systemd-timesyncd?

systemd-timesyncd is a lightweight SNTP client for basic sync. chrony is a full NTP implementation that can serve time, handle hardware refclocks, support NTS, and provide sub-millisecond accuracy. Use chrony for servers, timesyncd for minimal desktops/containers.

Does ntpd support NTS?

No. The reference ntpd does not support NTS. Only chrony (v4.0+), NTPsec, and ntpd-rs support NTS. If you need authenticated time, switch to one of these.

What is ntpd-rs?

A modern NTP implementation written in Rust by Trifecta Tech Foundation. Memory-safe, NTS-capable, and production-ready since 2024. Good for security-sensitive environments that don't need hardware refclocks.

Can I run chrony and timesyncd at the same time?

No. Only one NTP service should manage the clock. When installing chrony, it automatically disables timesyncd. Verify with timedatectl status.

Verify Your NTP Client

After configuring or migrating, verify your sync is working correctly:

Run NTP Diagnostics Troubleshoot Daemon Issues