Regular verses Daylight Savings Time

rwotten@checkfree.com rwotten at checkfree.com
Wed Apr 24 08:59:00 CDT 2002


May I also suggest a regular running of hwclock?
I do this in cron -

00 06 * * * /sbin/hwclock --systohc

If you don't do this your BIOS clock will slowly drift from your system
time.
When you reboot your system time will get set to the BIOS clock, which may
be too far off for NTP to sync up.
(Or just too far out there - even if you aren't running NTP.)

To further reduce time synchronization issues put your NTP server in
/etc/ntp/step-tickers.
The start script will then run an "ntpdate" before starting the ntp daemon,
ensuring that your system time is pretty darn close to the ntp server time,
ensuring that you won't be too far out of whack for NTP to sync.

--
Rick Otten
O=='=+



                                                                                                             
                      Michael Solberg                                                                        
                      <msolberg at arches.ug        To:       linux-poweredge at dell.com                          
                      a.edu>                     cc:                                                         
                      Sent by:                   Subject:  RE: Regular verses Daylight Savings Time          
                      linux-poweredge-adm                                                                    
                      in at dell.com                                                                            
                                                                                                             
                                                                                                             
                      04/23/02 05:55 PM                                                                      
                                                                                                             
                                                                                                             




On Tue, 23 Apr 2002, Karl Zander wrote:

> Ok...I ran tzselect.  Choose the options for Americas, United States and
> Eastern Time zone (I am in Washington, DC).  But the server is still off
by
> an hour.   UTC is also off by an hour.   It is one hour behind like it is

> still on Regular time and does not know about Daylight Savings Time.
>
> If I do not use ntpd, where does RedHat Linux 7.2 get its time from?  The

> hardware clock in the BIOS?

Yes.  If you don't want to run ntpd, a single

# ntpdate [my time server]

Should sync you up and it normally knows about Daylight Savings Time.
(I'm sure it's more complicated than just knowing, but it's always worked
for me on whichever linux I happened to be running. :-) ) It's always good
to run ntpd though, because it's important to keep your logs in order in
case something goes wrong.


>
> Karl Zander
>
> At 11:36 AM 4/23/2002 -0500, you wrote:
> >Run the command:   tzselect   then choose your Country (i.e. Americas,
> >Option 2), then choose United States - Option 45, then choose Option 9
for
> >Central Time.  It will then give you a confirmation on the Date & Time.
> >
> >
> >Jeremy Sheard
> >DELL Server Support
> >
> >-----Original Message-----
> >From: Robert Berlinger [mailto:rnb at aecom.yu.edu]
> >Sent: Tuesday, April 23, 2002 11:15 AM
> >To: Matt_Domsch at exchange.dell.com; KZander at commpartners.com
> >Cc: linux-poweredge at exchange.dell.com
> >Subject: RE: Regular verses Daylight Savings Time
> >
> >
> >Actually NTP syncs to UTC -- it doesn't deal with daylight savings.  The
> >conversion to local wall clock time is done by library routines.
> >
> >I don't know the answer either -- I believe it has to do with the
> >settings in /etc/localtime (which is binary data).  Normally this is set
> >during the system setup -- I don't know how to modify it subsequently.
> >(man tzfile talks about it from a technical standpoint).
> >
> >-----Original Message-----
> >From: linux-poweredge-admin at dell.com
> >[mailto:linux-poweredge-admin at dell.com] On Behalf Of
> >Matt_Domsch at dell.com
> >Sent: Tuesday, April 23, 2002 11:46 AM
> >To: KZander at commpartners.com
> >Cc: linux-poweredge at dell.com
> >Subject: RE: Regular verses Daylight Savings Time
> >Importance: Low
> >
> > > My 1400 server with RedHat 7.2 seems not to have recognized
> > > the switch to
> > > Daylight Savings Time.  Do I have to go into the BIOS to set
> > > the time?  Did
> > > I maybe miss something when setting up RedHat 7.2?  I do not
> > > recall having this problem with RedHat 6.2.
> >
> >I use ntpd to keep the time synchronized.  That worked great!  (The BIOS
> >doesn't know about time zones or daylight savings time.)
> >
> >Thanks,
> >Matt
> >
> >--
> >Matt Domsch
> >Sr. Software Engineer
> >Dell Linux Solutions www.dell.com/linux
> >Linux on Dell mailing lists @ http://lists.us.dell.com
> >#1 US Linux Server provider for 2001!
> >
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