[CentOS] Updating hardware clock from cron

Kwan Lowe kwan.lowe at gmail.com
Sat Mar 5 09:58:38 UTC 2011

On Fri, Mar 4, 2011 at 3:04 PM, Denniston, Todd A CIV NAVSURFWARCENDIV
Crane <todd.denniston at navy.mil> wrote:
> If your hwclock is off by a lot when it comes up I believe it is from
> one of the following:
> A) bad cmos battery.
> B) poor cmos clock
> C) confusing info in /etc/adjtime due to using both hwclock --adjust [at
> boot] and ntp (long story, but it is due to both tweaking the clock
> without coordination between them).
> D) booting a different OS with different ideas of timezones.
> E) manual tweaking of time via bios.

good list..  I'd also add "F) Running inside a virtual machine."

The VMWare clock skew can be enormous. On some systems it drifts by a
minute per hour if not adjusted via ntp.

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