adjtime - Linux

Overview

adjtime is a Linux command that allows users to modify and retrieve the system’s time and date. It provides precise control over the kernel’s timekeeping mechanisms, making it useful for fine-tuning accuracy or synchronizing with external time sources.

Syntax

adjtime [-k | -s] [offset]

Options/Flags

-k: Read and display the current time offset.
-s [offset]: Modify the current time offset. The offset is specified in milliseconds and can be either positive or negative.

Examples

Retrieve the current time offset:
```
adjtime -k
```
Adjust the time by 100 milliseconds:
```
adjtime -s 100
```
Set the time offset to -200 milliseconds:
```
adjtime -s -200
```

Common Issues

Insufficient privileges: You must have root privileges to use adjtime.
Invalid offset: The offset must be within a reasonable range (typically ±1000 milliseconds).
Time drift: Setting the time offset can cause time drift, so it should be used sparingly.

Integration

adjtime can be integrated into scripts or cron jobs for automated time adjustments. For example, to sync with an external NTP server every hour:

0 */1 * * * /usr/sbin/adjtime -s "$(ntpdate -q -b)"

Related Commands

ntpdate: Synchronizes the system clock with an NTP server.
hwclock: Modifies and retrieves the hardware clock.
date: Displays and sets the system date and time.