In-depth, last of chapter 06, LFS-4.0.

Bill maltby - LFS Related lfsbill at wlmcs.com
Sun Oct 6 11:37:36 PDT 2002


On Sun, 6 Oct 2002, Timothy Bauscher wrote:

> On Sun, Oct 06, 2002 at 02:36:41AM -0400, Bill maltby - LFS Related wrote:
> > T,
> > 
> > Sorry I haven't been more prompt on this. [...]

> Thanks Bill. I left the setclock description (bootscripts
> page) alone because, as it appeared to me, your description
> of setclock had a different meaning then the book version.
> Feel free to correct me though :P

Exactly. In the script the system clock is set regardless. Hwclock will be
called, with either the --utc or --localtime parameter, and the --hctosys
parameter.

But it is significant only if the HWC and system time are set to different
time zones. For Linux systems (especially CVS-involved development work-
stations), the HWC is normally set to UTC (GMT) and the system time is
normally set to local. So, for purposes of the description, it seemed that
the mention of the setting is significant when it sets the system clock to
a time (zone) different than the HWC (UTC/GMT).

If a user runs Win*, the HWC will most likely be set to local time. So, no
adjustment is needed. Again, the revised text seems more appropriate for
this condition because then no "perceived" adjustment is done.

So, the net result is that the kernel time is set to localtime regard-
less. Therefore, the text had significance only if the HWC was *not* set
to localtime, meaning that it was set to UTC/GMT. If this view is correct,
then the suggested text seems more appropriate.

BTW, AFAIK, this only affects the interpretation of the two clocks, not
their actual values. IOW, the system time is really the same as the HWC,
but is interpolated with the /etc/localtime (/usr/share/zoneinfo) setting
when being used for certain things, like the date command. For other
things, like CVS timestamps (AFAIK), the interpolation is not done.

Given the above, the previous wording seemed wrong to me. Maybe more
knowledgeable folks out there should comment? Oops! Need to show what we
are talking about. Remember that the system system clock is *always* set,
but that's significant, in relation to the description, only if the HWC
is set to a different zone than the system time.

setclock

  From:
    The setclock scripts resets the kernel clock to localtime in case the
    hardware clock isn't set to GMT time.
  To:
    The setclock scripts resets the kernel clock to localtime if the
    hardware clock is set to GMT time.

-- 
Bill Maltby
billm at wlmcs.com

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