How to Use the Command 'sntp' (with examples)

The Simple Network Time Protocol (SNTP) is a streamlined version of the Network Time Protocol (NTP), which is widely used for synchronizing clocks of networked systems. Being a lightweight client, sntp is used primarily to query an SNTP server for the correct time and, optionally, synchronize the local system clock. This command is important for ensuring that systems use accurate timekeeping, which is crucial for logging, security protocols, and network-based applications.

Use case 1: Query a specified SNTP server and display the time

Code:

sntp pool.ntp.org

Motivation:

Querying an SNTP server to display the time is often used to verify the current time setting of a system without making any changes to the system clock. This is especially useful for monitoring and auditing purposes, or when troubleshooting time-sensitive applications to ensure that the system time aligns with the standardized global time provided by reliable NTP sources.

Explanation:

• sntp: This is the command being used to query an SNTP server.
• pool.ntp.org: This is a widely used and reliable pool of NTP servers. By specifying this server, the sntp command will retrieve and display the current time according to an external reference, ensuring that the time information is accurate and up-to-date.

Example Output:

2023-10-18 15:45:53.123456 +00:00

The output shows the current synchronized time received from the specified SNTP server in Coordinated Universal Time (UTC) format.

Use case 2: Synchronize the system clock with a specified SNTP server

Code:

sudo sntp -S pool.ntp.org

Motivation:

Synchronizing the system clock with an SNTP server is crucial for maintaining time accuracy across different systems and networks. This is vital for tasks that require precise timing, such as distributed databases, automated transactions, and system logging. Ensuring that the system clock is in sync reduces errors and improves the reliability of operations across interconnected systems.

Explanation:

• sudo: This is a command that allows a permitted user to run a command as the superuser or another user. It is necessary here because modifying the system’s clock typically requires root or administrative privileges.
• sntp: The command that facilitates the query and synchronization.
• -S: The -S flag is used specifically to not only query the time from the SNTP server but also to set the system clock based on this queried time.
• pool.ntp.org: The chosen SNTP server pool from which to synchronize the system time.

Example Output:

synchronizing local clock to pool.ntp.org (123.45.67.8)
local clock synchronized to pool.ntp.org (offset: +0.001 seconds)

This output indicates that the local system clock has been successfully synchronized with the SNTP server, and it provides the corresponding server IP address and any time offset obtained during synchronization.

Use case 3: Enable debug logging

Code:

sntp -d pool.ntp.org

Motivation:

Enabling debug logging is particularly useful for diagnosing issues that may arise during time synchronization. This level of logging allows system administrators to review detailed information regarding the communication between the client and the SNTP server, elaborating on the process and any potential discrepancies in the data received. Debug logs can be invaluable during the troubleshooting of network issues or irregularities in time synchronization.

Explanation:

• sntp: This is the command used to interact with the SNTP server.
• -d: The -d flag signals that debug logging should be enabled. This means the command will provide verbose output, offering a deeper insight into its operations and the data received from the SNTP server.
• pool.ntp.org: This is the NTP server pool from which debug information will be logged.

Example Output:

17 Oct 15:55:25 sntp[12345]: querying pool.ntp.org
17 Oct 15:55:26 sntp[12345]: received Li=0, Stratum=2, Precision=-23, Root Delay=0.026477
17 Oct 15:55:26 sntp[12345]: receive timestamp: 0x83aa7b2c.dab856d9
17 Oct 15:55:26 sntp[12345]: time is 2023-10-18 16:55:26.902345 +00:00 (offset: +0.000123 sec)

The output provides detailed logs of the process, showing the query action, the server’s response in NTP format, the details of the time synchronization, and any difference (offset) from the local time.

Conclusion:

The sntp command is a powerful yet simple tool for interacting with SNTP servers. Whether for querying system time, synchronizing system clocks, or enabling detailed logging for troubleshooting, sntp fulfills essential timekeeping functions crucial for the smooth operation of networked systems. By leveraging this command effectively, system administrators can ensure precision and reliability in time-sensitive operations.