$ Linux Command

Network

ntpdate

Set system time by synchronizing with NTP servers.

ntptimesynchronizationclocknetwork

Additional Notes

ntpdate sets the local system clock by contacting one or more Network Time Protocol (NTP) servers. It performs a single time synchronization event, querying the servers for the correct time and adjusting the system clock to match. It is a one-shot alternative to running a full NTP daemon.

On many modern distributions, ntpdate has been deprecated in favor of ntpd -q, chronyd -q, timedatectl, or the systemd-timesyncd service. However, ntpdate remains useful for quick, manual time synchronization, especially during initial system setup, recovery from clock drift, or in environments where a persistent NTP daemon is not desired.

Syntax

ntpdate [options] [server...]

Parameters

  • server: One or more NTP server hostnames or IP addresses.

Common Options

  • -q: Query only. Display the time offset without setting the clock.
  • -s: Reduce output by logging via syslog instead of standard output.
  • -u: Use unprivileged ports, which can bypass some firewall restrictions.
  • -b: Step the time immediately with settimeofday (instead of gradually adjusting).
  • -B: Force clock slew using adjtime even if the offset is large.
  • -t timeout: Set the timeout for each NTP response in seconds (default 1).
  • -p samples: Specify the number of NTP samples to get from each server (default 4).
  • -d: Enable debug mode with verbose output.

Examples

ntpdate pool.ntp.org

Synchronize the system clock with the NTP pool.

ntpdate -q pool.ntp.org

Query the time without changing the system clock.

ntpdate -s ntp.ubuntu.com pool.ntp.org

Synchronize with multiple servers, sending output to syslog.

ntpdate -u pool.ntp.org

Use unprivileged ports to synchronize, useful behind restrictive firewalls.

ntpdate -b pool.ntp.org

Force an immediate time step instead of a gradual slew.

Practical Notes

  • ntpdate requires either root privileges or the CAP_SYS_TIME capability to set the system clock.
  • On systems running systemd-timesyncd or chronyd, running ntpdate concurrently can cause conflicts. Stop the time service first or use timedatectl set-ntp false.
  • Most distributions now recommend timedatectl for time management: timedatectl set-ntp true enables automatic synchronization.
  • For persistent NTP synchronization, use chrony (preferred on RHEL/CentOS/Fedora) or ntpd (traditional NTP daemon) instead of scheduling ntpdate via cron.
  • The -u option is useful on systems where NTP port 123 is blocked by a firewall or already in use.