Ubuntu Time Synchronization Explained: ntpdate, systemd-timesyncd, and Best Practices

1. Why Time Synchronization Is Important on Ubuntu

1.1 Time Is a Core System Primitive on Linux Servers

In Linux environments such as Ubuntu, time is not merely display information but a fundamental system assumption.
Internally, nearly all system processes operate based on the current system time. If this time is inaccurate, it can cause far more serious problems than it appears at first glance.

Ubuntu is widely used for server and cloud workloads, and time drift directly impacts the following areas:

1.2 Concrete Problems Caused by Time Drift

Log Integrity Breaks Down

System logs and application logs are all recorded with timestamps.
If the system clock is incorrect:

• The order of errors becomes unclear
• Troubleshooting becomes difficult
• Logs across multiple servers cannot be correlated

This is especially critical in distributed systems, where even slight time desynchronization can make troubleshooting virtually impossible.

SSL Certificates and Security Features Fail

SSL/TLS certificates used in HTTPS communications strictly verify validity periods.
If the server time is incorrect:

• “Certificate is not valid”
• “Certificate is not yet valid”

errors may occur, and connections may be rejected entirely.

This affects not only web servers, but also API communications and package management tools such as apt.

cron and systemd Timers Misbehave

Ubuntu commonly uses the following for scheduled tasks:

• cron
• systemd timers

If the system time is incorrect:

• Expected jobs do not run
• Tasks execute at unintended times

This can lead to subtle yet critical failures, such as missed backups or failed batch jobs.

1.3 Why This Matters Especially in Cloud and VPS Environments

Modern Ubuntu deployments typically run on:

• VPS
• Cloud (IaaS)
• Virtual machines

In these environments, time management is separated between host and guest operating systems, and drift may occur due to:

• Virtualization overhead
• Suspend/resume cycles
• Clock delays under high load

It is not uncommon for time to drift by several minutes without notice.

For these reasons, Ubuntu is designed around automatic and continuous time synchronization.

1.4 Why So Many People Search for “ntpdate”

When time drift occurs, many users search for:
“ubuntu time synchronization”
“ubuntu ntpdate”

This is because:

• ntpdate used to be the standard tool
• Large amounts of outdated documentation still exist
• It appears to offer a quick one-command fix

However, modern Ubuntu has fundamentally changed its approach to time synchronization, and running ntpdate is no longer the recommended solution.

2. What Is ntpdate?

2.1 The Basic Role of ntpdate

ntpdate is a legacy command-line tool for time synchronization that has been used in Linux environments for many years.
It queries a specified NTP server and synchronizes the system clock only once.

Its key characteristics are:

• Does not run as a daemon
• Adjusts time immediately when executed
• Extremely simple configuration

Because of this simplicity, many users viewed it as a quick fix during incidents.

2.2 How ntpdate Works

The internal behavior of ntpdate is straightforward:

1. Query the current time from an NTP server
2. Calculate the difference from the local system time
3. Apply the correction immediately

This allows instant correction for drifts ranging from seconds to minutes.

However, because it forcibly adjusts the system clock, it can negatively affect running processes and services.

2.3 Difference Between ntpdate and ntpd

ntpdate is often confused with ntpd (the NTP daemon), but their roles differ clearly.

• ntpdate
  • One-time execution
  • Immediate time adjustment
  • Not resident
• ntpd (NTP daemon)
  • Runs continuously
  • Gradually corrects time
  • Designed for long-term stability

From an operational standpoint, resident services are safer, and ntpdate has always been a supplementary tool.

3. Why “ubuntu ntpdate” Is Still Searched

3.1 Users Search Because Something Is Already Broken

The search term “ubuntu ntpdate” usually indicates that a time synchronization issue has already occurred.

Typical triggers include:

• SSL errors on servers
• cron jobs not running
• Incorrect log timestamps
• Package update failures

In such situations, users naturally search for quick fixes.

3.2 Outdated Information Remains Abundant

Because ntpdate was used for so long, large volumes of outdated content still exist:

• Old blog posts
• Q&A site answers
• Technical books
• Posts on Qiita and Stack Overflow

Many of these sources recommend running ntpdate without explaining version context, leading users to execute it blindly.

3.3 The Gap with Official Ubuntu Documentation

Current Ubuntu documentation assumes:

• systemd-timesyncd is enabled by default
• Time synchronization is automatic and continuous
• Manual intervention is usually unnecessary

However, beginners often think:

• “What is systemd?”
• “That sounds complicated”
• “I need to fix this immediately”

As a result, they gravitate toward ntpdate because it appears simpler and faster.

4. Handling of ntpdate by Ubuntu Version

4.1 ntpdate in the Ubuntu 16.04 / 18.04 Era

During the Ubuntu 16.04 and 18.04 era,
ntpdate was a practical and commonly used option.

Key characteristics of this period included:

• The ntpdate package existed in official repositories
• Frequently used together with ntpd
• Widely used for initial synchronization and troubleshooting

Especially right after server provisioning, when:

• The system clock was significantly off
• ntpd had not yet stabilized

ntpdate was considered extremely convenient.

4.2 The Shift That Began with Ubuntu 18.04

Starting with Ubuntu 18.04,
systemd began to be fully adopted internally.

This architectural shift introduced:

• Time management integration into systemd
• An assumption of resident, automatic synchronization
• A reduced role for one-shot synchronization tools

Although ntpdate was still available at this stage,
it was no longer considered essential.

4.3 The Decisive Change in Ubuntu 20.04 and Later

From Ubuntu 20.04 onward, the situation changed significantly.

• systemd-timesyncd enabled by default
• ntpdate not installed by default
• Clear classification as deprecated

As a result, running ntpdate with the old mindset now causes:

• Command not found errors
• Missing package issues
• Conflicts with systemd

The key takeaway is that
Ubuntu fully shifted its design philosophy from “one-shot synchronization” to “continuous synchronization”.

4.4 The Current State in Ubuntu 22.04 / 24.04

In Ubuntu 22.04 and 24.04, this policy is even clearer.

• Time synchronization is automatic
• Administrator involvement is minimal
• Manual synchronization is unnecessary in most cases

As a result, ntpdate rarely appears in official documentation.

Instead, the primary tools are:

• systemd-timesyncd
• chrony (for advanced use cases)

4.5 Confusion Caused by Ignoring Version Differences

Many issues arise from situations such as:

• Applying old Ubuntu knowledge to newer versions
• Search results that omit version assumptions
• Lack of awareness about the installed Ubuntu release

This often leads to questions like:

“Why does this no longer work even though it used to?”

In reality, this is a natural consequence of Ubuntu’s evolution.

4.6 Summary of Version-Based Perspective

In short:

• 16.04 / 18.04 → ntpdate was practical
• 20.04 and later → ntpdate is generally unnecessary
• 22.04 / 24.04 → Continuous synchronization is assumed

5. Recommended Time Synchronization Methods on Modern Ubuntu

5.1 Ubuntu’s Standard Design: Automatic Continuous Synchronization

On modern Ubuntu systems,
time is not something administrators manually adjust, but something automatically maintained.

The core mechanism behind this is systemd-integrated time synchronization.

• Automatically synchronizes at boot
• Continuously fine-tunes during runtime
• Enabled by default without special configuration

In most environments,
accurate time synchronization is already working.

5.2 Using systemd-timesyncd (Default Configuration)

What Is systemd-timesyncd?

systemd-timesyncd is a
lightweight NTP client built into systemd.

Its characteristics include:

• Resident service with automatic synchronization
• Very simple configuration
• Optimized for Ubuntu’s default setup

Unless you have specific requirements,
this is the correct choice.

Checking Time Synchronization Status

You can check the current status with the following command:

timedatectl

Pay particular attention to:

• System clock synchronized
• NTP service

If these are enabled,
time synchronization is already functioning correctly.

Enabling NTP Synchronization

If NTP is disabled, you can enable it with:

sudo timedatectl set-ntp true

This immediately starts automatic synchronization via systemd-timesyncd.

Notes on Synchronization Timing

systemd-timesyncd is designed to avoid:

• Large, abrupt time jumps
• Frequent aggressive corrections

Therefore, when:

• The clock is significantly off
• The network has just come online

you may need to wait several minutes for full synchronization.

5.3 When to Use chrony

What Is chrony?

chrony is a
high-precision, high-reliability time synchronization solution.

It is commonly used in environments such as:

• Servers
• Long-running systems
• Unstable network conditions
• Virtualized or containerized environments

Difference from systemd-timesyncd

The differences can be summarized as follows:

• systemd-timesyncd
  • Lightweight
  • Simple configuration
  • General-purpose usage
• chrony
  • High precision
  • Fine-grained control
  • Server-oriented operation

For desktops and small servers,
systemd-timesyncd is usually sufficient.

When chrony Is Appropriate

Consider chrony if:

• Time accuracy directly affects business requirements
• You operate your own NTP servers
• Time drift occurs frequently in virtualized environments

However,
there is no need to choose chrony merely as a “replacement for ntpdate”.

5.4 Why Resident Services Are Recommended

Modern Ubuntu favors resident synchronization for clear reasons:

• Avoids abrupt time changes
• Minimizes service disruption
• Reduces human error

This aligns with a
server design philosophy that prioritizes stability.

6. If You Still Want to Use ntpdate

6.1 How to Decide Whether ntpdate Is Necessary

As a general rule,
there is almost no need to use ntpdate in normal operation.

However, it may be considered temporarily in cases such as:

• Immediately after initial system provisioning
• systemd-timesyncd fails to synchronize
• Resident services are intentionally disabled
• Testing or short-lived environments requiring immediate correction

In other words, ntpdate should be viewed as
an emergency measure, not a permanent solution.

6.2 Typical Temporary Use Cases

Immediately After OS Installation

After creating a virtual machine or VPS:

• The clock may be off by minutes or more
• systemd-timesyncd may not have synchronized yet

In such cases, running ntpdate once,
then handing control back to a resident service,
is a reasonable approach.

When the Clock Is Severely Off

Time can become severely inaccurate due to:

• Battery depletion
• Virtualization platform issues
• Manual clock changes

In such situations,
resident NTP services may not recover gracefully,
and ntpdate may be used once to reset the clock.

6.3 Installing and Using ntpdate

On Ubuntu 20.04 and later, ntpdate is not installed by default.
To use it, you must install it explicitly.

sudo apt update
sudo apt install ntpdate

Example usage:

sudo ntpdate pool.ntp.org

This synchronizes the system time with the specified NTP server.

Keep in mind that this action is temporary.

6.4 Beware of Conflicts with systemd

The biggest risk when using ntpdate is
conflict with resident services such as systemd-timesyncd.

Running both simultaneously can lead to:

• Unclear authoritative time source
• Unexpected time changes
• Negative impact on logs and services

Therefore, when using ntpdate:

• Limit usage to temporary situations
• Return to resident synchronization afterward
• Never use it continuously

6.5 Why ntpdate Should Not Be Used Regularly

Although convenient, ntpdate is disadvantaged in modern Ubuntu environments:

• Abrupt time adjustments
• No consideration for running services
• Conflicts with automatic management philosophy

As a result,
what starts as an occasional fix can become a source of instability.

6.6 Correct Positioning Summary

ntpdate has shifted from:

• Formerly a primary tool
• Now a supplementary utility
• Generally unnecessary

With this understanding,
it can be used calmly and appropriately when truly needed.

7. Common Errors and How to Handle Them

7.1 When ntpdate: command not found Appears

Meaning of the Error

This error indicates that the ntpdate command does not exist on the system.
On Ubuntu 20.04 and later, this is not an abnormal condition but expected behavior.

In most cases, this occurs because:

• ntpdate is not installed by default
• The tool is deprecated and intentionally omitted

How to Think About the Fix

When this error appears, the first question should be:

“Do I really need ntpdate?”

• If systemd-timesyncd is enabled, ntpdate is unnecessary
• If automatic synchronization is working, no action is required

Rather than installing ntpdate simply because it is missing,
prioritizing methods aligned with modern Ubuntu design is the correct approach.

7.2 When no server suitable for synchronization found Appears

Meaning of the Error

This error means that communication with the NTP server failed.

Possible causes include:

• No network connectivity
• DNS resolution failure
• Firewall blocking traffic
• The specified NTP server not responding

Points to Check

When this error occurs, verify the following in order:

• Internet connectivity is available
• DNS resolution is functioning
• UDP port 123 is not blocked

Although it appears to be an NTP issue,
it is often actually a network configuration problem.

7.3 When systemd-timesyncd Does Not Synchronize

Common Misconceptions

It is easy to assume “the system is broken” when time is incorrect,
but systemd-timesyncd does not guarantee immediate synchronization.

• Right after boot
• Immediately after network connection
• When the clock is significantly off

Synchronization may take some time in these situations.

How to Assess the Situation

First, confirm whether:

• NTP is enabled
• The service is running
• No error state is reported

In many cases,
waiting briefly is sufficient for synchronization to complete naturally.

7.4 Time Drift Specific to Virtual Environments

Why Virtual Machines Drift More Easily

In virtual environments, time instability is common due to:

• Host OS influence
• CPU scheduling variability
• Suspend and resume cycles

This is not a flaw in Ubuntu itself,
but a characteristic of virtualization platforms.

Basic Mitigation Strategy

In virtual environments:

• Enable resident time synchronization
• Avoid repeated one-shot corrections
• Ensure the host system time is accurate

This approach minimizes long-term drift.

7.5 Why “Just Run ntpdate” Should Be Avoided

When errors occur, it is tempting to simply run ntpdate,
but this rarely resolves the underlying issue.

• The root cause lies elsewhere
• The problem often recurs
• The approach contradicts system design

Especially during failures,
understanding the mechanisms Ubuntu is designed around is critical.

7.6 Error Handling Summary

When dealing with time synchronization issues, consider the following order:

1. Is automatic synchronization enabled?
2. Is the network functioning correctly?
3. Is the approach appropriate for the Ubuntu version?
4. Is an emergency workaround truly necessary?

Keeping this sequence in mind prevents being misled by ntpdate.

8. Conclusion: The Correct Way to Think About Time Synchronization on Ubuntu

8.1 ntpdate Was Once Correct, but Is No Longer the Main Tool

In earlier Ubuntu and Linux environments,
ntpdate was the standard solution for time synchronization.

• Simple and easy to understand
• Immediate correction
• Useful as an emergency fix

As a result, it remains strongly embedded in search results and user memory.

However, modern Ubuntu systems have
fundamentally changed their architecture.

8.2 Modern Ubuntu Assumes Automatic, Continuous Synchronization

From Ubuntu 20.04 onward, the baseline design includes:

• systemd-based unified management
• Resident NTP synchronization
• Maintenance without manual intervention

This means that operations such as:

• Manually fixing time
• Running periodic commands

are no longer expected.

8.3 The First Check Should Be “Is It Already Synchronized?”

When time-related issues occur,
the first step should not be:

• Searching for ntpdate
• Executing commands immediately

Instead, verify:

• Whether automatic synchronization is enabled
• Whether systemd-timesyncd is running

In many cases,
the system is already correct or will self-correct shortly.

8.4 If You Use ntpdate, Do So Only Temporarily

There are still scenarios where ntpdate may be appropriate:

• Immediately after initial provisioning
• When the clock is severely inaccurate
• Testing or temporary environments

Even then, it is essential to:

• Avoid continuous use
• Return to automatic synchronization afterward
• Prevent conflicts with resident services

ntpdate is now best understood as
a supplementary tool for exceptional cases only.

8.5 Avoiding Confusion Around “ubuntu ntpdate”

The most important message of this article can be summarized as:

If you need to search for ntpdate on Ubuntu, the situation itself is already exceptional

Understanding this prevents:

• Being misled by outdated articles
• Overreacting to error messages
• Making unnecessary configuration changes

8.6 Correct Choices Lead to Stable Operations

Time synchronization may seem mundane,
but it is the foundation of system reliability.

• Trust automatic synchronization
• Understand modern Ubuntu design
• Update outdated operational knowledge

This mindset leads to stable and reliable Ubuntu systems.

9. Frequently Asked Questions (FAQ)

Q1. Is ntpdate no longer usable on Ubuntu?

It is not completely unusable,
but in modern Ubuntu it is not installed by default and is classified as deprecated.

From Ubuntu 20.04 onward, automatic resident synchronization via systemd-timesyncd is the standard,
making ntpdate unnecessary for normal operation.

Q2. What is the difference between ntpdate and ntpd?

Their roles are different:

• ntpdate: Forces a one-time clock adjustment
• ntpd: Runs continuously and gradually corrects time

On modern Ubuntu systems,
systemd-timesyncd or chrony replaces ntpd.

Q3. Should I use systemd-timesyncd or chrony?

For most environments, systemd-timesyncd is sufficient.

chrony is more suitable when:

• Time accuracy directly affects business requirements
• The system runs continuously for long periods
• Time drift frequently occurs in virtual environments

You do not need to choose chrony simply as a replacement for ntpdate.

Q4. Why does time drift occur more often in virtual machines?

Virtual environments are more susceptible to drift due to:

• Host OS timing behavior
• CPU scheduling variability
• Suspend and resume cycles

Therefore,
enabling resident automatic synchronization is essential.

Q5. Time is incorrect even though systemd-timesyncd is enabled

systemd-timesyncd is designed to avoid abrupt clock changes.

As a result, synchronization may take time when:

• The system has just booted
• The network has just connected
• The clock is significantly off

In most cases,
waiting briefly resolves the issue naturally.

Q6. Are there situations where using ntpdate is acceptable?

Yes, in limited scenarios such as:

• Immediately after OS installation
• When the clock is severely incorrect
• Temporary testing environments

However, continuous use should be avoided,
and automatic synchronization should be restored afterward.

Q7. How can I disable time synchronization if needed?

In special testing environments, NTP can be disabled intentionally.

However, this is intended for exceptional use cases,
and is not recommended for production systems.

Disabling synchronization increases the risk of:

• SSL errors
• Log inconsistencies
• Scheduled task failures

Q8. What should beginners remember?

Beginners only need to remember three points:

1. Ubuntu is designed for automatic time synchronization
2. ntpdate is no longer the mainstream approach
3. Always check automatic synchronization first

With this knowledge,
confusion around “ubuntu ntpdate” becomes rare.