[mdlug] Can the date stamp on a file be ahead of the clock

[Raymond McLaughlin]

Robert Meier wrote:

> I assume you meant to say "the system clock is used for file system
> time stamps", as the file timestamp matched the date(1) setting
> in your example above.

Er, yes that's right.

> Ray> I've read the relevant man pages repeatedly and still don't
> Ray> really see the point of keeping two different clocks. I just
> Ray> keep mine synchronized. First I use the date command to set
> Ray> the system clock, then I run (as root of course):
> Ray>    ->hwclock --systohc
> 
> The reason for the two clocks is convenience, performance and
> volatility.  The hardware clock keeps time even when the system
> is shutdown.   The system clock is available to the kernel (and
> its filesystem drivers) millions of times per second if necessary
> without the overhead of an i/o interface.
> 
> You can operate a unix system without a hardware clock,
> if you simply set the system clock from another source (e.g.
> network time server) each time you boot.
> 
> Accurate time is the defacto standard for coordinating network services
> like email, source file sharing and remote makes.
> 
> A hardware clock, consulted at boot (and otherwise occasionally)
> is so cheap a motherboard acccessory, that its rare to find a
> motherboard without one.

Thanks for the explanation.