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Best Practices on setting clock? - Linux / Unix Administration

I am running a UNIX operating system on a PC and I did set my CMOS or the Hardware Clock to use the system time as UTC while the operating system clock or the DISPLAYED TIME is set to local time adjusted from the CMOS clock in the BIOS which is in UTC. So I would like to ask everyone out here as to which is the best amd more preferrable time or clock settings to use on UNIX systems? 1. Should I leave the RTC or Hardware Clock as UTC and set the DISPLAYED TIME as LOCAL TIME? 2. ...

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  1. #1

    Default Best Practices on setting clock?

    I am running a UNIX
    operating system on a PC and I did set my CMOS or the Hardware Clock to
    use the system time as UTC while the operating system clock or the
    DISPLAYED TIME is set to local time adjusted from the CMOS clock in the
    BIOS which is in UTC.

    So I would like to ask everyone out here as to which is the best amd
    more preferrable time or clock settings to use on UNIX systems?

    1. Should I leave the RTC or Hardware Clock as UTC and set the
    DISPLAYED TIME as LOCAL TIME?

    2. Or, set the DISPLAYED TIME as UTC time also while keeping the
    Internal or CMOS clock as UTC too?

    I was told one time, that in large corporate datacenters that use UNIX,
    there kept in UTC. But are they referring to the Internal Clock, or the
    actual operating system clock?

    I would greatly appreciate the help in advance. This is very important
    to me.

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    a.vincze@yahoo.com Guest

  2. #2

    Default Re: Best Practices on setting clock?

    When people say the best time setting for UNIX is UTC...do they mean
    the BIOS RTC Clock or the actual displayed OS time??


    com wrote: 

    a.vincze@yahoo.com Guest

  3. #3

    Default Re: Best Practices on setting clock?

    Have a look here - a bit dated, but still quite relevant:
    news:7i9mjb$crl.com

    com wrote: 

    They could be addressing either and/or both. The RTC is the first
    thing of note that's often easier and/or more practical to have set
    to UTC (and pretty much only feasible to use UTC, for many types of
    UNIX hardware).

    UTC is also quite advantageous for logs and cross-timezone related
    communications (e.g. when system is used, or timestamps need to be
    referenced and/or correlated, across multiple timezones).

    In UNIX(/LINUX/BSD/...) the system clock is logically related to UTC -
    specifically, it keeps track of seconds since the UNIX epoch (00:00
    1970-01-01 UTC). Essentially all times in UNIX are determined by
    converting to/from seconds from the epoch. When a UNIX system is
    booted, under normal cirstances, relatively early in the boot
    process, the system time is set based upon the time found on the
    hardware RTC. Many UNIX flavors also have some utilities to
    set/adjust the RTC - but once booted, the RTC is often relatively
    independent of the system time. E.g. on UNIX systems, date(1) and
    stime(1) can be used to set the system time, but in many
    cases, they do not set or alter the RTC.
     [/ref]

    Michael Guest

  4. #4

    Default Re: Best Practices on setting clock?

    Thanks alot...Lot of information you gave me....
    Question...Whats the appropirate proceedure on a dual-boot Windows/UNIX
    system time settings??

    1. Do i need to set the CMOS clock to UTC and the actual OS or diplayed
    time would be LOCAL TIME according to my local Time Zone?

    2. Next question...what time proceedures do all the Government systems
    use as far as them running UNIX machines? Do they have the RTC clock
    set to UTC and the OS displayed time as local time? Or, do they run
    both as UTC??

    3. Last question - Someone told me to make life so much easier for UNIX
    system admins is to have their UNIX servers run UTC. In general, in a
    production environment like a data centre, it is better to keep all
    servers in UTC (or Zulu) time. Then ensure that all front-end
    applications manage the display of the time depending on where the
    disply is appearing. It will make your your life SOOOOO much easier.

    But does that actually mean to have the servers have their RTC clock
    set to UTC and the applications logs are dispplayed in local times??
    What does this actually mean in # 3 ??

    Thanks

    Please advise...


    com wrote: 

    a.vincze@yahoo.com Guest

  5. #5

    Default Re: Best Practices on setting clock?

    And also --- Is it wise to log all UNIX applications in UTC? Or, just
    keep the RTC Hardware clock to UTC and let the applications log in
    LOCAL TIME??


    com wrote: 

    a.vincze@yahoo.com Guest

  6. #6

    Default Re: Best Practices on setting clock?

    On 16 Apr 2006 08:53:39 -0700, com wrote: 

    You will have to decide what you want the hardware clock to have.

    You then tell the OSs what you picked. Pretty straight forward.
    When a Unix/linux box shuts down, it sets the hardware clock to the
    system time. When the Unix/linux boots up it sets system time to value
    read from the hardware clock.

    On my dual boot systems, XP Home understand I have it set UTC, on my
    win98 it does not show local time correcty.

    Since Micro$oft made me buy it's OS when I bought the system I set my
    ntpd service to fetch time sync values from time.windows.com.
    Bit Guest

  7. #7

    Default Re: Best Practices on setting clock?

    1. Ok, I am dual-booting with Windows2000/Solaris 10 on Interl...My
    CMOS clock or Hardware Clock is set to UTC...(which I wanted it to
    be)....In Solaris, the actual DISPLAYED time in the desktop is set to
    Local Time...

    2. Windows 2000 DISPLAYED desktop time or clock is set to LOCAL...And
    then under those properties, I have this box checked to Adjust clock
    Automatically for DST" CHECKED...And I also created this registry tweak
    called: RealTimeIsUniversal =1 to tell Windows that the CMOS clock or
    Hardware clock is to UTC...My question is, will these settings cause
    any problems during a DST change?

    3. Also, I forgot to ask this. Military systems that run UNIX (e.g.
    Trusted Solaris, HP-UX), are those systems kept on UTC time both for
    Hardware clock and the actual displayed clocks? Or, its only the
    Hardware clock that is set to UTC and the actual displayed times are in
    Local Time? Or, both?

    I have numbered my questions for you to provide or reply to each ones.
    I would appreciate it.

    Thanks in advance!!

    com wrote: 

    a.vincze@yahoo.com Guest

  8. #8

    Default Re: Best Practices on setting clock?

    com wrote: 

    UNIX cares about the *time* not the settings. If you only run UNIX
    use the UNIX standard of setting the *time* to UTC and use timezones.
    If you dual boot (you do according to another message) then other
    operating systems care.
     

    The deal is, UNIX doesn't know or care if there's a CMOS clock
    or a time-of-year clock or whatever. The fact that a PC has two
    concepts of time isn't something that UNIX is interested in.

    But PC operating systems are designed and built for PC
    hardware. They know and care. As a result you should set the
    CMOS clock to local time because that's what a PC operating
    system expects. Then inform UNIX of what the offset is.
     

    In UNIX there isn't any difference whatsoever between the two.
    But are they referring to the ones or the zeroes? It's a question
    with the same lack of meaning.
     

    It doesn't make sense that timezone issues should be all that
    important. They are so easily set.

    Doug Guest

  9. #9

    Default Re: Best Practices on setting clock?

    I am sorry, but I am still lost at a bat here.

    Ok,

    1. If I would be using UNIX as the only OS in a PC, you mean I should
    set the CMOS or RTC clock in UTC and have the actual displayed time on
    my desktop to use local time if I set the local Time Zone? Or, BOTH the
    RTC or Hardware clock and the Desktop clock should be both UTC? I am
    located in the PDT Time Zone..

    2. In order to prevent issues during DST on dual boot Windows
    2000/Solaris PCs, what be the MOST ideal for setting the time for both
    the RTC clock and the clock that sit on the desktop?

    a.vincze@yahoo.com Guest

  10. #10

    Default Re: Best Practices on setting clock?

    And according to Casper Dik's weblog..(do a google search) and select
    Solaris and then scroll down to were it says Timezone and
    Multi-boot...In a dual-boot Windows/Solaris system, this is what you
    should you in order to prevent issues with DST. So according to these
    instructions, the RTC SHOULD be se to UTC in a dual-boot OS system..But
    here, Im getting answers that this should be the other way around....

    Set the following registry key (it does not exist!)

    HKLM/SYSTEM/CurrentControlSet/Control/TimeZoneInformation/RealTimeIsUniversal
    (REG_DWORD = 1)

    In the control panel with Day&Time settings, check the
    "automatically adjust" check box.


    Boot into Solaris and run:


    rtc -c -z UTC

    then correct the clock with date/rdate
    (if you use liveupgrade, lumount your other partition(s) and
    copy the
    /etc/rtc_config file to all of them)

    In Linux, you'll need to run "timeconfig" and select "RTC set
    to GMT".

    a.vincze@yahoo.com Guest

  11. #11

    Default Re: Best Practices on setting clock?

    com wrote: 

    It's a judgement call. Casper Dik's job is to work through such
    issues and come up with best practices based on many
    experiences. I've worked a bit with dual-boot machines and I
    came to a different opinion. Thinking over that difference and
    why the difference is there, I'll take Casper Dik's word and
    defer.
     

    Doug Guest

  12. #12

    Default Re: Best Practices on setting clock?

    I am still getting mixed responses and I am in a limbo here again on to
    which is the best method or ideal method for setting time on Dual-boots
    like Windows and Solaris..To avoid this DST observance issued on both
    OSs, what needs to be done here?

    1. If I would be using UNIX as the only OS in a PC, you mean I should
    set the CMOS or RTC clock in UTC and have the actual displayed time on
    my desktop to use local time if I set the local Time Zone? Or, BOTH the
    RTC or Hardware clock and the Desktop clock should be both UTC? I am
    located in the PDT Time Zone..

    2. In order to prevent issues during DST on dual boot Windows
    2000/Solaris PCs, what be the MOST ideal for setting the time for both
    the RTC clock and the clock that sit on the desktop?

    a.vincze@yahoo.com Guest

  13. #13

    Default Re: Best Practices on setting clock?

    I need to have a concrete answer into all of this..

    a.vincze@yahoo.com Guest

  14. #14

    Default Re: Best Practices on setting clock?

    On 17 Apr 2006 12:38:14 -0700, com <com> wrote: 

    Bloody hell. Set your clock with Windows. Boot into Unix. Adjust your
    timezone offset as needed. The end.

    Dave Guest

  15. #15

    Default Re: Best Practices on setting clock?

    RTC or the H/W clock is already set to UTC as I checked the BIOS. Also
    my desktop clock is set to Local time...SOlaris is also set already to
    local PDT time as TZ=US/Pacific...

    Finally, I got it right....This should be the right way when dual
    booting other OSs..

    a.vincze@yahoo.com Guest

  16. #16

    Default Re: Best Practices on setting clock?

    RTC or the H/W clock is already set to UTC as I checked the BIOS. Also
    my desktop clock is set to Local time...SOlaris is also set already to
    local PDT time as TZ=US/Pacific...

    Finally, I got it right....This should be the right way when dual
    booting other OSs..

    a.vincze@yahoo.com Guest

  17. #17

    Default Re: Best Practices on setting clock?

    RTC or the H/W clock is already set to UTC as I checked the BIOS. Also
    my Windows desktop clock is set to Local time...SOlaris is also set
    already to
    local PDT time as TZ=US/Pacific...

    Finally, I got it right....This should be the right way when dual
    booting other OSs..

    a.vincze@yahoo.com Guest

  18. #18

    Default Re: Best Practices on setting clock?

    You mean to leave my BIOS or RTC clock in UTC and have both desktop
    clocks adjusted to local timezone?

    a.vincze@yahoo.com Guest

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