rdate Command in Linux

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rdate is a command used in Linux to set the system date and time by querying a remote server. This command is particularly useful for synchronizing your system clock with an external time source, ensuring that your system time is accurate.

Table of Contents

Here is a comprehensive guide to the options available with the rdate command −

• Installing of rdate Command in Linux
• Syntax of rdate Command
• rdate Command Options
• Examples of rdate Command in Linux

Installing of rdate Command in Linux

Linux systems generally do not come with the rdate command preinstalled. You can install it using the package manager that is available on your system.

For Debian-based systems (like Ubuntu) −

sudo apt install rdate

For Red Hat-based systems (like CentOS) −

sudo yum install rdate

For Arch Linux −

sudo pacman -S rdate

Syntax of rdate Command

To execute the rdate command in Linux, use the following basic syntax −

rdate [options] [hostname]

Where −

• [options] are optional parameters that alter the command's functionality.
• [hostname] is the remote server from which the date and time will be retrieved.

rdate Command Options

Here are some various options you can use with the Linux rdate command −

Examples of rdate Command in Linux

Below are a few examples demonstrating how to use the rdate command in different scenarios on a Linux environment −

• Setting System Time Using IPv4
• Displaying Retrieved Data Over IPv6
• Using Gradual Adjustment with adjtime
• Setting Time with a Threshold
• Synchronizing Time Using SNTP
• Verbose Output

Setting System Time Using IPv4

To set your system's date and time using a remote server over IPv4, run the following command −

rdate -4 -s time.nist.gov

This command queries the time.nist.gov server using IPv4 and updates your system's clock to match the time retrieved from the server.

Displaying Retrieved Date Over IPv6

If you only want to see the date and time from a remote server using IPv6 without changing your system's clock, use this command −

rdate -6 -p time.nist.gov

Executing this command will print the current date and time from time.nist.gov over an IPv6 connection without modifying your system's settings.

Using Gradual Adjustment with adjtime

To gradually adjust your system's time using adjtime, you can use the following command −

rdate -a time.nist.gov

This command retrieves the time from time.nist.gov and applies the changes gradually, smoothing out the adjustment over time.

Setting Time with a Threshold

If you want to use an immediate change only if the time difference exceeds a certain threshold, you can use this command −

rdate -b 60 time.nist.gov

This command will use an immediate change if the time difference with time.nist.gov is greater than 60 seconds; otherwise, it will adjust gradually.

Synchronizing Time Using SNTP

To synchronize your system's clock using the SNTP protocol, run the following command −

rdate -n time.nist.gov

This command queries the time.nist.gov server using SNTP and updates your system's clock accordingly.

Verbose Output

For more detailed information during the synchronization process, you can enable verbose output with this command −

rdate -v time.nist.gov

This command provides additional details about the time synchronization process, making it easier to debug any issues.

Conclusion

The rdate command is a valuable tool for keeping your system's date and time synchronized with an external time source. By understanding the syntax, available options, and practical examples, you can effectively use rdate to ensure your system's clock is accurate.

In this tutorial, we provided the necessary information to utilize rdate efficiently and maintain correct system time.