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MachineOfTheMonth: Setting the clock in Linux

Mar 24, 2000, 22:29 (0 Talkback[s])
(Other stories by Glenn Mullikin)

"Does your computer tell time correctly? With Linux, there are two different clocks. The system clock and the hardware clock. I wouldn't presume to be an expert on this subject but out of necessity, I had to learn a little about how they function so that I could get the right time on my system. It was all messed up for a long time."

"What would happen is when the computer booted up, the time was wrong. Then I would use the date command (man date) to try and set it correctly but then whenever the computer was rebooted (I turn my computer off at night) the wrong time was again in the system. Very big problem. But how do you fix this? The hardware clock, as the name implies, is the one that keeps running even when your computer's power supply is turned off. CMOS clock, Real Time Clock, these are names or synonyms for the hardware clock. Do a man hwclock for more information on this. The system clock is what Linux uses to reference the date and time, basically. It does not go directly to the hardware clock. So for instance, with Debian and I would assume any other distribution, it first sets the system time on boot up using the hardware clock. (hwclock --hctosys). And then upon shutdown, my Debian system is set up to transfer the system time back to the hardware clock. So there it is. So how do you set the date and time if you wish to?..."

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