Detailed explanation of hwclock command

hwclock Introduction

The hwclock command is used to set or read the system hardware clock. This clock is usually a battery-powered clock on the computer's motherboard.

Set the clock

To set the hardware clock, use the following syntax:

hwclock --set --date="MMDDhhmm[[[[cc]yy]]]"

Where:

• --set:Specifies to set the clock.
• --date:followed by the date and time to be set.
• MM:Month (for example, 01 means January)
• DD:Day (for example, 01 means 1st)
• hh:Hours (for example, 01 means 1 o'clock)
• mm:Minutes (for example, 01 means 1 minute)
• cc:Century (for example, 20 for the 21st century)
• yy:Year (for example, 20 for 2020)

For example, to To set the hardware clock to January 1, 2023, 12:00 AM, use the following command:

hwclock --set --date="010100002023"

Read Clock

To read the hardware clock, Just enter the following command:

hwclock

It will print the current clock value in your console.

Options

The hwclock command also provides the following options:

• --localtime:Display time as local time.
• --utc:Displays the time as Coordinated Universal Time (UTC).
• --show:Only displays the current time and does not set anything.
• --backup:Back up the current time to a file.
• --restore:The time to restore the previous backup from the file.
• --systohc:Synchronize the system clock to the hardware clock.
• --hctoys:Synchronize the hardware clock to the system clock.

Example

To synchronize the hardware clock with the system clock, use the following command:

hwclock --systohc

To copy from filetimebackupTo restore the time of a previous backup, use the following command:

hwclock --restore --file=/path/to/timebackup

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