Re: Network Time Protocol Daemon needed for zLinux?
I have enjoyed this discussion of NTP (etc.) and then just saw this on /. http://tech.slashdot.org/story/15/03/20/1731209/internet-of-things-endangered-by-inaccurate-network-time-says-nist Thought everyone might enjoy. Regards, Jeff -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: Network Time Protocol Daemon needed for zLinux?
On 15Mar19:0045-0400, Alan Altmark wrote: But you must be careful. If you think about this too hard, you will create a tear in the time-space continuum and fall in. Just remember that The music is reversible, but time is not. Kcab nrut, kcab nrut, What is it about computers and their clocks that after so many decades, we still struggle with getting this right? We can leave the politicians and their local time games out of this. Why does the world standard need to be concerned with the sun's position at exactly noon anyway--why not let just the applications that have a need to know (does that include GPS?) deal with it? The engineering issues been resolved, but we still can't build consensus globally for a proper standard. Am I the only person who considers this state of affairs embarrassing? -- not cent from sell May the LORD God bless you exceedingly abundantly! Dave_Craig__ So the universe is not quite as you thought it was. You'd better rearrange your beliefs, then. Because you certainly can't rearrange the universe. __--from_Nightfall_by_Asimov/Silverberg_ -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: Network Time Protocol Daemon needed for zLinux?
None of this has anything to do with the sun's position .. it's having computers all over the world show the same time at whatever moment during the day or night you choose. Timezones are just offsets to that. Scott Rohling On Thu, Mar 19, 2015 at 5:48 AM, David L. Craig dlc@gmail.com wrote: On 15Mar19:0045-0400, Alan Altmark wrote: But you must be careful. If you think about this too hard, you will create a tear in the time-space continuum and fall in. Just remember that The music is reversible, but time is not. Kcab nrut, kcab nrut, What is it about computers and their clocks that after so many decades, we still struggle with getting this right? We can leave the politicians and their local time games out of this. Why does the world standard need to be concerned with the sun's position at exactly noon anyway--why not let just the applications that have a need to know (does that include GPS?) deal with it? The engineering issues been resolved, but we still can't build consensus globally for a proper standard. Am I the only person who considers this state of affairs embarrassing? -- not cent from sell May the LORD God bless you exceedingly abundantly! Dave_Craig__ So the universe is not quite as you thought it was. You'd better rearrange your beliefs, then. Because you certainly can't rearrange the universe. __--from_Nightfall_by_Asimov/Silverberg_ -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/ -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: Network Time Protocol Daemon needed for zLinux?
On Thursday, 03/19/2015 at 08:49 EDT, David L. Craig dlc@gmail.com wrote: On 15Mar19:0045-0400, Alan Altmark wrote: But you must be careful. If you think about this too hard, you will create a tear in the time-space continuum and fall in. Just remember that The music is reversible, but time is not. Kcab nrut, kcab nrut, What is it about computers and their clocks that after so many decades, we still struggle with getting this right? We can leave the politicians and their local time games out of this. Why does the world standard need to be concerned with the sun's position at exactly noon anyway--why not let just the applications that have a need to know (does that include GPS?) deal with it? The engineering issues been resolved, but we still can't build consensus globally for a proper standard. Am I the only person who considers this state of affairs embarrassing? The problem is fundamentally that time of day is a human concept. All computers can do is count - they can't tell time. Even the atomic clocks just measure very tiny intervals of time (t1-t0). So we invented epochs (the time of day represented by time t0=0). A natural thing to do since all you have is a hammer, eh? That meant the current time can be calculated based on how many intervals of time (e.g. seconds) have passed. But the assumption there is that the number of seconds in a day is a constant. Drats. That ruined everything. Why? Because you can't just arbitrarily add leap seconds into a calculation. Sometimes you want an interval (e.g. wait 10 seconds) and sometimes you want a specific time (Wake up at 12:00). When all times are elapsed, you often end up computing specific times using epoch + interval math. Enter leap second, stage right. Is that timer that is scheduled to pop at 12:00 the result of a time of day or an interval? G! Feh. Conceptually, there is such a thing as a UTC TOD clock, where there are separate fields for year, month, day, seconds and fractions of seconds. Leap seconds are handled by simply delaying the increment of the day field until the seconds counter is 61. Time math is a lot easier since the TOD clock is already in a format that allows for instructions that do the proper math for you. Alan Altmark Senior Managing z/VM and Linux Consultant Lab Services System z Delivery Practice IBM Systems Technology Group ibm.com/systems/services/labservices office: 607.429.3323 mobile; 607.321.7556 alan_altm...@us.ibm.com IBM Endicott -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: Network Time Protocol Daemon needed for zLinux?
Ugh -- read that as a 'tad longer' ... I SO wish for edit capability sometimes. It would help eliminate corrective posts for brain farts like this. Scott Rohling On Thu, Mar 19, 2015 at 8:45 AM, Scott Rohling scott.rohl...@gmail.com wrote: True - if only we'd made a 'normal' second just a tad larger ;-) It would be fun to see the 'correct seconds' and 'sidereal time' folks fight it out! All I know is it's almost time for lunch ... Scott Rohling On Thu, Mar 19, 2015 at 8:31 AM, Rick Troth ri...@velocitysoftware.com wrote: On 03/19/2015 10:28 AM, Scott Rohling wrote: None of this has anything to do with the sun's position .. it's having computers all over the world show the same time at whatever moment during the day or night you choose. Timezones are just offsets to that. Methinks the leap seconds are celestially motivated. Otherwise, yes!, apply and offset and then trust z TOD. I suggested ntpdate at periodic (long) intervals for situations where the earth moved under your feet. It happens. -- Rick Troth Senior Software Developer Velocity Software Inc. Mountain View, CA 94041 Main: (877) 964-8867 Direct: (614) 594-9768 ri...@velocitysoftware.com mailto:ri...@velocitysoftware.com Signature http://www.velocitysoftware.com/ *Follow us:* Facebook http://www.facebook.com/pages/Velocity-Software/356098274460840 LinkedIn http://www.linkedin.com/company/1798379 Twitter http://www.twitter.com/VelocitySoftw Xing http://www.xing.com/companies/velocitysoftwaregmbh -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/ -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: Network Time Protocol Daemon needed for zLinux?
Its celestially motivated. Computers only care about the number of ticks since the start of some arbitrary epoch. P.S. I got the ELO reference. * * -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: Network Time Protocol Daemon needed for zLinux?
Folks, With a leap second occurring EOD June 30th, 2015, for sites choosing to use ntp, running the latest SuSE and Red Hat releases, when the ntpd daemon was configured with the -x option to adjust the system clock slowly instead of changing the time instantaneously, the system clock was incorrectly changed instantaneously when a leap second occurred. This was very recently addressed ntp.org opened Bug 2745 - Summary: ntpd -x steps clock on leap second http://bugs.ntp.org/show_bug.cgi?id=2745 and released ntp-4.2.6p5-xleap.patch http://pkgs.fedoraproject.org/cgit/ntp.git/tree/ntp-4.2.6p5-xleap.patch Red Hat has released an ntp RHBA-2015:0690-1 https://rhn.redhat.com/errata/RHBA-2015-0690.html containing this patch and my understanding is that SuSE will do this in it's coming maintenance release. Mike O'Reilly IBM Linux Change Team PS ... I've watched every Dr. Who episode and time still confuses me. Rick Troth rickt@velocityso ftware.comTo Sent by: Linux on LINUX-390@VM.MARIST.EDU 390 Port cc linux-...@vm.mar IST.EDU Subject Re: Network Time Protocol Daemon needed for zLinux? 03/19/2015 08:31 AM Please respond to Linux on 390 Port linux-...@vm.mar IST.EDU On 03/19/2015 10:28 AM, Scott Rohling wrote: None of this has anything to do with the sun's position .. it's having computers all over the world show the same time at whatever moment during the day or night you choose. Timezones are just offsets to that. Methinks the leap seconds are celestially motivated. Otherwise, yes!, apply and offset and then trust z TOD. I suggested ntpdate at periodic (long) intervals for situations where the earth moved under your feet. It happens. -- Rick Troth Senior Software Developer Velocity Software Inc. Mountain View, CA 94041 Main: (877) 964-8867 Direct: (614) 594-9768 ri...@velocitysoftware.com mailto:ri...@velocitysoftware.com Signature http://www.velocitysoftware.com/ *Follow us:* Facebook http://www.facebook.com/pages/Velocity-Software/356098274460840 LinkedIn http://www.linkedin.com/company/1798379 Twitter http://www.twitter.com/VelocitySoftw Xing http://www.xing.com/companies/velocitysoftwaregmbh -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/ -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: Network Time Protocol Daemon needed for zLinux?
Linux on 390 Port LINUX-390@VM.MARIST.EDU wrote on 03/19/2015 11:31:55 AM: Methinks the leap seconds are celestially motivated. Otherwise, yes!, apply and offset and then trust z TOD. I suggested ntpdate at periodic (long) intervals for situations where the earth moved under your feet. It happens. Rick you're correct. Time is relative to motion, the faster something travels the slower time progresses. This has been proven as more than a theory on the space shuttle when they had two synchronized time sources one on the earth and one on the shuttle. when the shuttle landed the time sources where compared and the one on the shuttle did in fact move slower. it's was microseconds (it was only traveling 18K MPH) but that proved that theory. Expand on that and the earth revolves around the sun and it's not a constant speed. as we come into summer and are in our closer orbit we travel faster and during the winter we travel slower at the further distances. That's why summers go so fast and winters never seem to end and the reason IMHO for leap seconds. It's either that or it's one big conspiracy theory to see if the government can get it's people to do something as dumb as changing our clocks twice a year. Sandra -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: Network Time Protocol Daemon needed for zLinux?
But the point here is that it shouldn't be necessary on Linux under z/VM if STP has been implemented and the z obtains it's time from an NTP server... it's redundancy that might make things worse. It's not like you are going to take your zLinux image and run it on x86 ... so to me it makes sense to have platform (or environment) specific differences in your builds. If you haven't implemented STP, then my point is moot :) Scott Rohling On Thu, Mar 19, 2015 at 8:02 AM, Martha McConaghy u...@vm.marist.edu wrote: We do the same thing, but for a different reason. We want all of our Linux servers to be coordinated to the same time, no matter what platform they are running on. Makes syslog processing easier. Martha On Wed, 18 Mar 2015 20:57:02 + Marcy Cortes said: We run NTP on all the Linux guests under zVM (and we have STP for VM). There were just too many things that require it and it wasn't worth the effort to make them believe that it wasn't necessary. -Original Message- From: Linux on 390 Port [mailto:LINUX-390@VM.MARIST.EDU] On Behalf Of Vitale, Joseph Sent: Wednesday, March 18, 2015 1:00 PM To: LINUX-390@VM.MARIST.EDU Subject: Re: [LINUX-390] Network Time Protocol Daemon needed for zLinux? Using STP to set clock for zVM LPAR. zVM and zLinux guest show time, both in sync. Trying to avoid setting up NTPD and starting on all zLinux if not necessary. Came about due to checks comparing zLinux software configuration vs X86 configuration, they run NTPD. So, I was asked to do same. Never seen an issue with time under zLinux. Thank you for your assistance Joe Joseph Vitale Technology Services Group Mainframe Operating Systems Pershing Plaza 95 Christopher Columbus Drive Floor 14 Jersey City, N.J. 07302 Work 201-395-1509 Cell917-903-0102 -Original Message- From: Linux on 390 Port [mailto:LINUX-390@VM.MARIST.EDU] On Behalf Of Rob van der Heij Sent: Wednesday, March 18, 2015 3:54 PM To: LINUX-390@VM.MARIST.EDU Subject: Re: Network Time Protocol Daemon needed for zLinux? On 18 March 2015 at 20:04, Vitale, Joseph joseph.vit...@bnymellon.com wrote: My Linux runs under zVM, not in a stand alone LPAR. So, NTP or STP not required, correct ? That depends on whether you have STP steer the clock for the LPARs. It's a priced feature. If Q TIME on z/VM is now very accurate, then you're most likely steering and your Linux guests will follow. When z/VM is not running on time, then all Linux guests will get a clock (the same) that is slightly off as well. If that bothers you (your applications rather) then you can either implement STP or have each guest synchronize it's won clock with ntpd etc. If you frequently reboot, then ntpdate during startup might be enough to stay somewhat on time (eg 3 seconds per week). Some things like Kerberos expect you to be sort-of on time (10's of seconds, iirc). My experience is that the quality of the clock with ntpd is somewhat less, but that's a moot point when it's your only option. Yes, it's true that running ntpd takes resources. But much middleware does too and we're not on G3 anymore. PS Yes, I did do an ntpq for CMS a while back, but the year does not have nearly enough Friday nights to come up with an alternative for STP. Rob -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/ The information contained in this e-mail, and any attachment, is confidential and is intended solely for the use of the intended recipient. Access, copying or re-use of the e-mail or any attachment, or any information contained therein, by any other person is not authorized. If you are not the intended recipient please return the e-mail to the sender and delete it from your computer. Although we attempt to sweep e-mail and attachments for viruses, we do not guarantee that either are virus-free and accept no liability for any damage sustained as a result of viruses. Please refer to http://disclaimer.bnymellon.com/eu.htm for certain disclosures relating to European legal entities. -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/ -- For LINUX-390
Re: Network Time Protocol Daemon needed for zLinux?
On 03/19/2015 10:28 AM, Scott Rohling wrote: None of this has anything to do with the sun's position .. it's having computers all over the world show the same time at whatever moment during the day or night you choose. Timezones are just offsets to that. Methinks the leap seconds are celestially motivated. Otherwise, yes!, apply and offset and then trust z TOD. I suggested ntpdate at periodic (long) intervals for situations where the earth moved under your feet. It happens. -- Rick Troth Senior Software Developer Velocity Software Inc. Mountain View, CA 94041 Main: (877) 964-8867 Direct: (614) 594-9768 ri...@velocitysoftware.com mailto:ri...@velocitysoftware.com Signature http://www.velocitysoftware.com/ *Follow us:* Facebook http://www.facebook.com/pages/Velocity-Software/356098274460840 LinkedIn http://www.linkedin.com/company/1798379 Twitter http://www.twitter.com/VelocitySoftw Xing http://www.xing.com/companies/velocitysoftwaregmbh -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: Network Time Protocol Daemon needed for zLinux?
We do the same thing, but for a different reason. We want all of our Linux servers to be coordinated to the same time, no matter what platform they are running on. Makes syslog processing easier. Martha On Wed, 18 Mar 2015 20:57:02 + Marcy Cortes said: We run NTP on all the Linux guests under zVM (and we have STP for VM). There were just too many things that require it and it wasn't worth the effort to make them believe that it wasn't necessary. -Original Message- From: Linux on 390 Port [mailto:LINUX-390@VM.MARIST.EDU] On Behalf Of Vitale, Joseph Sent: Wednesday, March 18, 2015 1:00 PM To: LINUX-390@VM.MARIST.EDU Subject: Re: [LINUX-390] Network Time Protocol Daemon needed for zLinux? Using STP to set clock for zVM LPAR. zVM and zLinux guest show time, both in sync. Trying to avoid setting up NTPD and starting on all zLinux if not necessary. Came about due to checks comparing zLinux software configuration vs X86 configuration, they run NTPD. So, I was asked to do same. Never seen an issue with time under zLinux. Thank you for your assistance Joe Joseph Vitale Technology Services Group Mainframe Operating Systems Pershing Plaza 95 Christopher Columbus Drive Floor 14 Jersey City, N.J. 07302 Work 201-395-1509 Cell917-903-0102 -Original Message- From: Linux on 390 Port [mailto:LINUX-390@VM.MARIST.EDU] On Behalf Of Rob van der Heij Sent: Wednesday, March 18, 2015 3:54 PM To: LINUX-390@VM.MARIST.EDU Subject: Re: Network Time Protocol Daemon needed for zLinux? On 18 March 2015 at 20:04, Vitale, Joseph joseph.vit...@bnymellon.com wrote: My Linux runs under zVM, not in a stand alone LPAR. So, NTP or STP not required, correct ? That depends on whether you have STP steer the clock for the LPARs. It's a priced feature. If Q TIME on z/VM is now very accurate, then you're most likely steering and your Linux guests will follow. When z/VM is not running on time, then all Linux guests will get a clock (the same) that is slightly off as well. If that bothers you (your applications rather) then you can either implement STP or have each guest synchronize it's won clock with ntpd etc. If you frequently reboot, then ntpdate during startup might be enough to stay somewhat on time (eg 3 seconds per week). Some things like Kerberos expect you to be sort-of on time (10's of seconds, iirc). My experience is that the quality of the clock with ntpd is somewhat less, but that's a moot point when it's your only option. Yes, it's true that running ntpd takes resources. But much middleware does too and we're not on G3 anymore. PS Yes, I did do an ntpq for CMS a while back, but the year does not have nearly enough Friday nights to come up with an alternative for STP. Rob -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/ The information contained in this e-mail, and any attachment, is confidential and is intended solely for the use of the intended recipient. Access, copying or re-use of the e-mail or any attachment, or any information contained therein, by any other person is not authorized. If you are not the intended recipient please return the e-mail to the sender and delete it from your computer. Although we attempt to sweep e-mail and attachments for viruses, we do not guarantee that either are virus-free and accept no liability for any damage sustained as a result of viruses. Please refer to http://disclaimer.bnymellon.com/eu.htm for certain disclosures relating to European legal entities. -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/ -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/ -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
Re: Network Time Protocol Daemon needed for zLinux?
It's all just this wibbley wobbley timey whimey stuff... Lee Stewart ● VM System Support ● Visa ● Phone: 6(750)4601 - +1-303-389-4601 ● lstew...@visa.com -Original Message- From: Linux on 390 Port [mailto:LINUX-390@VM.MARIST.EDU] On Behalf Of Rick Troth Sent: Thursday, March 19, 2015 9:32 AM To: LINUX-390@VM.MARIST.EDU Subject: Re: Network Time Protocol Daemon needed for zLinux? On 03/19/2015 10:28 AM, Scott Rohling wrote: None of this has anything to do with the sun's position .. it's having computers all over the world show the same time at whatever moment during the day or night you choose. Timezones are just offsets to that. Methinks the leap seconds are celestially motivated. Otherwise, yes!, apply and offset and then trust z TOD. I suggested ntpdate at periodic (long) intervals for situations where the earth moved under your feet. It happens. -- Rick Troth Senior Software Developer Velocity Software Inc. Mountain View, CA 94041 Main: (877) 964-8867 Direct: (614) 594-9768 ri...@velocitysoftware.com mailto:ri...@velocitysoftware.com Signature http://www.velocitysoftware.com/ *Follow us:* Facebook http://www.facebook.com/pages/Velocity-Software/356098274460840 LinkedIn http://www.linkedin.com/company/1798379 Twitter http://www.twitter.com/VelocitySoftw Xing http://www.xing.com/companies/velocitysoftwaregmbh -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/ -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: Network Time Protocol Daemon needed for zLinux?
True - if only we'd made a 'normal' second just a tad larger ;-) It would be fun to see the 'correct seconds' and 'sidereal time' folks fight it out! All I know is it's almost time for lunch ... Scott Rohling On Thu, Mar 19, 2015 at 8:31 AM, Rick Troth ri...@velocitysoftware.com wrote: On 03/19/2015 10:28 AM, Scott Rohling wrote: None of this has anything to do with the sun's position .. it's having computers all over the world show the same time at whatever moment during the day or night you choose. Timezones are just offsets to that. Methinks the leap seconds are celestially motivated. Otherwise, yes!, apply and offset and then trust z TOD. I suggested ntpdate at periodic (long) intervals for situations where the earth moved under your feet. It happens. -- Rick Troth Senior Software Developer Velocity Software Inc. Mountain View, CA 94041 Main: (877) 964-8867 Direct: (614) 594-9768 ri...@velocitysoftware.com mailto:ri...@velocitysoftware.com Signature http://www.velocitysoftware.com/ *Follow us:* Facebook http://www.facebook.com/pages/Velocity-Software/356098274460840 LinkedIn http://www.linkedin.com/company/1798379 Twitter http://www.twitter.com/VelocitySoftw Xing http://www.xing.com/companies/velocitysoftwaregmbh -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/ -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: Network Time Protocol Daemon needed for zLinux?
On 03/18/2015 11:46 AM, Vitale, Joseph wrote: Currently not running NTPD under RedHat, is that necessary or does zVM present time adjustment via Sysplex Timer? Given the stability of the z System clock, good practice is to run 'ntpdate' shortly after Linux boots and then perhaps at (long) intervals. Performance opinions vary. I found that 'ntpd' is one of the better behaved daemons in terms of load. Originally I told customers kill it. But I no longer insist on this. (Always a good idea to minimize the number of tasks running on a guest.) My teammate Rob van der Heij may have additional details to share. Alan Altmark explained some of the STP behavior over on the IBMVM list just last week. Perhaps he can chime in on this too. -- Rick Troth Senior Software Developer Velocity Software Inc. Mountain View, CA 94041 Main: (877) 964-8867 Direct: (614) 594-9768 ri...@velocitysoftware.com mailto:ri...@velocitysoftware.com -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: Network Time Protocol Daemon needed for zLinux?
On Wed, Mar 18, 2015 at 10:46 AM, Vitale, Joseph joseph.vit...@bnymellon.com wrote: Hello, Currently not running NTPD under RedHat, is that necessary or does zVM present time adjustment via Sysplex Timer? I think this answers that question: http://www-01.ibm.com/support/knowledgecenter/linuxonibm/com.ibm.linux.z.lgdd/lgdd_r_feature_time.html quote ETR- and STP-based clock synchronization Your Linux instance might be part of an extended remote copy (XRC) setup that requires synchronization of the Linux time-of-day (TOD) clock with a timing network. Linux on z Systems supports external time reference (ETR) and system time protocol (STP) based TOD synchronization. ETR and STP work independently of one another. If both ETR and STP are enabled, Linux might use either to synchronize the clock. For more information about ETR, see the IBM® Redbooks® technote at www.ibm.com/redbooks/abstracts/tips0217.html For information about STP, see www.ibm.com/systems/z/advantages/pso/stp.html Both ETR and STP support are included in the Linux kernel. No special build options are required. ETR requires at least one ETR unit that is connected to an external time source. For availability reasons, many installations use a second ETR unit. The ETR units correspond to two ETR ports on Linux. Always set both ports online if two ETR units are available. Attention: Be sure that a reliable timing signal is available before enabling clock synchronization. With enabled clock synchronization, Linux expects regular timing signals and might stop indefinitely to wait for such signals if it does not receive them. Enabling clock synchronization when booting Use kernel parameters to enable clock synchronization when booting. Enabling and disabling clock synchronization You can use the sysfs interfaces of ETR and STP to enable and disable clock synchronization on a running Linux instance. Parent topic: System resources /quote Thanks Joe -- If you sent twitter messages while exploring, are you on a textpedition? He's about as useful as a wax frying pan. 10 to the 12th power microphones = 1 Megaphone Maranatha! John McKown -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Network Time Protocol Daemon needed for zLinux?
Hello, Currently not running NTPD under RedHat, is that necessary or does zVM present time adjustment via Sysplex Timer? Thanks Joe Joseph Vitale Technology Services Group Mainframe Operating Systems Pershing Plaza 95 Christopher Columbus Drive Floor 14 Jersey City, N.J. 07302 Work 201-395-1509 Cell917-903-0102 The information contained in this e-mail, and any attachment, is confidential and is intended solely for the use of the intended recipient. Access, copying or re-use of the e-mail or any attachment, or any information contained therein, by any other person is not authorized. If you are not the intended recipient please return the e-mail to the sender and delete it from your computer. Although we attempt to sweep e-mail and attachments for viruses, we do not guarantee that either are virus-free and accept no liability for any damage sustained as a result of viruses. Please refer to http://disclaimer.bnymellon.com/eu.htm for certain disclosures relating to European legal entities. -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: Network Time Protocol Daemon needed for zLinux?
Using STP to set clock for zVM LPAR. zVM and zLinux guest show time, both in sync. Trying to avoid setting up NTPD and starting on all zLinux if not necessary. Came about due to checks comparing zLinux software configuration vs X86 configuration, they run NTPD. So, I was asked to do same. Never seen an issue with time under zLinux. Thank you for your assistance Joe Joseph Vitale Technology Services Group Mainframe Operating Systems Pershing Plaza 95 Christopher Columbus Drive Floor 14 Jersey City, N.J. 07302 Work 201-395-1509 Cell917-903-0102 -Original Message- From: Linux on 390 Port [mailto:LINUX-390@VM.MARIST.EDU] On Behalf Of Rob van der Heij Sent: Wednesday, March 18, 2015 3:54 PM To: LINUX-390@VM.MARIST.EDU Subject: Re: Network Time Protocol Daemon needed for zLinux? On 18 March 2015 at 20:04, Vitale, Joseph joseph.vit...@bnymellon.com wrote: My Linux runs under zVM, not in a stand alone LPAR. So, NTP or STP not required, correct ? That depends on whether you have STP steer the clock for the LPARs. It's a priced feature. If Q TIME on z/VM is now very accurate, then you're most likely steering and your Linux guests will follow. When z/VM is not running on time, then all Linux guests will get a clock (the same) that is slightly off as well. If that bothers you (your applications rather) then you can either implement STP or have each guest synchronize it's won clock with ntpd etc. If you frequently reboot, then ntpdate during startup might be enough to stay somewhat on time (eg 3 seconds per week). Some things like Kerberos expect you to be sort-of on time (10's of seconds, iirc). My experience is that the quality of the clock with ntpd is somewhat less, but that's a moot point when it's your only option. Yes, it's true that running ntpd takes resources. But much middleware does too and we're not on G3 anymore. PS Yes, I did do an ntpq for CMS a while back, but the year does not have nearly enough Friday nights to come up with an alternative for STP. Rob -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/ The information contained in this e-mail, and any attachment, is confidential and is intended solely for the use of the intended recipient. Access, copying or re-use of the e-mail or any attachment, or any information contained therein, by any other person is not authorized. If you are not the intended recipient please return the e-mail to the sender and delete it from your computer. Although we attempt to sweep e-mail and attachments for viruses, we do not guarantee that either are virus-free and accept no liability for any damage sustained as a result of viruses. Please refer to http://disclaimer.bnymellon.com/eu.htm for certain disclosures relating to European legal entities. -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: Network Time Protocol Daemon needed for zLinux?
Just a warning: my understanding is that this quote is talking about Linux in LPAR; that z/VM does not virtualize the ETR/STP. For the rest of us: When you have STP steer the LPAR TOD to keep z/VM on time, Linux will inherit the same (UTC) TOD and runs better on time than anything you can do with ntpd. This will cover the leap second in that the TOD appears to slow down for a few hours, to be on time in the morning. On 18 March 2015 at 19:33, John McKown john.archie.mck...@gmail.com wrote: On Wed, Mar 18, 2015 at 10:46 AM, Vitale, Joseph joseph.vit...@bnymellon.com wrote: Hello, Currently not running NTPD under RedHat, is that necessary or does zVM present time adjustment via Sysplex Timer? I think this answers that question: http://www-01.ibm.com/support/knowledgecenter/linuxonibm/com.ibm.linux.z.lgdd/lgdd_r_feature_time.html quote ETR- and STP-based clock synchronization Your Linux instance might be part of an extended remote copy (XRC) setup that requires synchronization of the Linux time-of-day (TOD) clock with a timing network. Linux on z Systems supports external time reference (ETR) and system time protocol (STP) based TOD synchronization. ETR and STP work independently of one another. If both ETR and STP are enabled, Linux might use either to synchronize the clock. For more information about ETR, see the IBM® Redbooks® technote at www.ibm.com/redbooks/abstracts/tips0217.html For information about STP, see www.ibm.com/systems/z/advantages/pso/stp.html Both ETR and STP support are included in the Linux kernel. No special build options are required. ETR requires at least one ETR unit that is connected to an external time source. For availability reasons, many installations use a second ETR unit. The ETR units correspond to two ETR ports on Linux. Always set both ports online if two ETR units are available. Attention: Be sure that a reliable timing signal is available before enabling clock synchronization. With enabled clock synchronization, Linux expects regular timing signals and might stop indefinitely to wait for such signals if it does not receive them. Enabling clock synchronization when booting Use kernel parameters to enable clock synchronization when booting. Enabling and disabling clock synchronization You can use the sysfs interfaces of ETR and STP to enable and disable clock synchronization on a running Linux instance. Parent topic: System resources /quote Thanks Joe -- If you sent twitter messages while exploring, are you on a textpedition? He's about as useful as a wax frying pan. 10 to the 12th power microphones = 1 Megaphone Maranatha! John McKown -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/ -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: Network Time Protocol Daemon needed for zLinux?
hehe .. I do wonder if hypervisors on other platforms deal wiith this -- my guess is they just shrug and run ntpd on their guests. I do understand the mentality of running the same setup on every platform .. but it isn't that difficult to allow for the fact that you don't want packages installed and running that aren't necessary for the platform. And .. (IMO) there should be a difference between a virtual setup and a physical one. As you say - se la vi :) Scott Rohling On Wed, Mar 18, 2015 at 3:19 PM, Rob van der Heij rvdh...@gmail.com wrote: On 18 March 2015 at 23:02, Scott Rohling scott.rohl...@gmail.com wrote: Not sure how strongly you were asked :) -- but I would explain that z/VM-Linux are already synced with whatever NTP server the z is using.. and I would ask why it should then be necessary. Put the burden of explanation on them to tell you why it doesn't satisfy the time synch requirement. Scott Rohling Such is life. I remember a discussion with the Linux admin that went like this :-) R: You're running ntpd - you shouldn't when the hypervisor is already synchronized A: But I need the exact time, and that requires ntpd R: No, it does not. It's wasting resources and does not do you any good. A: I need it anyway, for exact time. R: Your time on z/Linux will be less exact with ntpd than without A: I does not have to be that exact, so I will run ntpd anyway -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/ -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: Network Time Protocol Daemon needed for zLinux?
On Wednesday, 03/18/2015 at 06:04 EDT, Rob van der Heij rvdh...@gmail.com wrote: Sorry to complicate it, but that check is not conclusive. When Linux does not run ntpd, the time on Linux will match the time on z/VM (give or take time zones). But when they still match the wall clock time a few weeks after the IPL of z/VM, you know STP is steering the clock. Someone said to me that they thought zLinux will still use jiffies in certain cases, which can cause now to have some significant variation. Perhaps Those Who Know will speak up. I've done more thinking, studying, and talking to Development about this, and I now believe that TOD clock steering does NOT deal with leap seconds. This is because the TOD clock is steered to Coordinated Server Time (CST), not UTC, and CST is computed by adding the leap seconds to UTC. UTC can be determined by manual input or from NTP. So if you set leap seconds to zero, you have UTC but only until the next leap second. But Development is inquiring of PE to verify. Architecturally, the z TOD clock is ahead of UTC by the number of leap seconds contained in the UTC clock. And please know, too, that it is the STP feature that steers the TOD clock to the external time source. Without it, you have to re-IPL z/VM to get the LPAR TOD clock resync'd with the physical TOD clock, which is adjusted to match the time obtained by the SE from the external time source at model-dependent intervals. Leap seconds become important when you start reaching back in the time. If you reach past the most recent leap second insertion point, the wall clock or TOD clock conversations start being off by one second per insertion. For many things, that's close enough. For others (e.g. financial institutions) the time standards are established by regulatory agencies. But you must be careful. If you think about this too hard, you will create a tear in the time-space continuum and fall in. Just remember that The music is reversible, but time is not. Kcab nrut, kcab nrut, Alan Altmark Senior Managing z/VM and Linux Consultant Lab Services System z Delivery Practice IBM Systems Technology Group ibm.com/systems/services/labservices office: 607.429.3323 mobile; 607.321.7556 alan_altm...@us.ibm.com IBM Endicott -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: Network Time Protocol Daemon needed for zLinux?
My Linux runs under zVM, not in a stand alone LPAR. So, NTP or STP not required, correct ? Thanks Joseph Vitale Technology Services Group Mainframe Operating Systems Pershing Plaza 95 Christopher Columbus Drive Floor 14 Jersey City, N.J. 07302 Work 201-395-1509 Cell917-903-0102 -Original Message- From: Linux on 390 Port [mailto:LINUX-390@VM.MARIST.EDU] On Behalf Of Rob van der Heij Sent: Wednesday, March 18, 2015 2:53 PM To: LINUX-390@VM.MARIST.EDU Subject: Re: Network Time Protocol Daemon needed for zLinux? Just a warning: my understanding is that this quote is talking about Linux in LPAR; that z/VM does not virtualize the ETR/STP. For the rest of us: When you have STP steer the LPAR TOD to keep z/VM on time, Linux will inherit the same (UTC) TOD and runs better on time than anything you can do with ntpd. This will cover the leap second in that the TOD appears to slow down for a few hours, to be on time in the morning. On 18 March 2015 at 19:33, John McKown john.archie.mck...@gmail.com wrote: On Wed, Mar 18, 2015 at 10:46 AM, Vitale, Joseph joseph.vit...@bnymellon.com wrote: Hello, Currently not running NTPD under RedHat, is that necessary or does zVM present time adjustment via Sysplex Timer? I think this answers that question: http://www-01.ibm.com/support/knowledgecenter/linuxonibm/com.ibm.linux .z.lgdd/lgdd_r_feature_time.html quote ETR- and STP-based clock synchronization Your Linux instance might be part of an extended remote copy (XRC) setup that requires synchronization of the Linux time-of-day (TOD) clock with a timing network. Linux on z Systems supports external time reference (ETR) and system time protocol (STP) based TOD synchronization. ETR and STP work independently of one another. If both ETR and STP are enabled, Linux might use either to synchronize the clock. For more information about ETR, see the IBM(r) Redbooks(r) technote at www.ibm.com/redbooks/abstracts/tips0217.html For information about STP, see www.ibm.com/systems/z/advantages/pso/stp.html Both ETR and STP support are included in the Linux kernel. No special build options are required. ETR requires at least one ETR unit that is connected to an external time source. For availability reasons, many installations use a second ETR unit. The ETR units correspond to two ETR ports on Linux. Always set both ports online if two ETR units are available. Attention: Be sure that a reliable timing signal is available before enabling clock synchronization. With enabled clock synchronization, Linux expects regular timing signals and might stop indefinitely to wait for such signals if it does not receive them. Enabling clock synchronization when booting Use kernel parameters to enable clock synchronization when booting. Enabling and disabling clock synchronization You can use the sysfs interfaces of ETR and STP to enable and disable clock synchronization on a running Linux instance. Parent topic: System resources /quote Thanks Joe -- If you sent twitter messages while exploring, are you on a textpedition? He's about as useful as a wax frying pan. 10 to the 12th power microphones = 1 Megaphone Maranatha! John McKown -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/ -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/ The information contained in this e-mail, and any attachment, is confidential and is intended solely for the use of the intended recipient. Access, copying or re-use of the e-mail or any attachment, or any information contained therein, by any other person is not authorized. If you are not the intended recipient please return the e-mail to the sender and delete it from your computer. Although we attempt to sweep e-mail and attachments for viruses, we do not guarantee that either are virus-free and accept no liability for any damage sustained as a result of viruses. Please refer to http://disclaimer.bnymellon.com/eu.htm for certain disclosures relating to European legal entities. -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390
Re: Network Time Protocol Daemon needed for zLinux?
On 18 March 2015 at 21:00, Vitale, Joseph joseph.vit...@bnymellon.com wrote: Using STP to set clock for zVM LPAR. zVM and zLinux guest show time, both in sync. Trying to avoid setting up NTPD and starting on all zLinux if not necessary. Sorry to complicate it, but that check is not conclusive. When Linux does not run ntpd, the time on Linux will match the time on z/VM (give or take time zones). But when they still match the wall clock time a few weeks after the IPL of z/VM, you know STP is steering the clock. Rob -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: Network Time Protocol Daemon needed for zLinux?
Not sure how strongly you were asked :) -- but I would explain that z/VM-Linux are already synced with whatever NTP server the z is using.. and I would ask why it should then be necessary. Put the burden of explanation on them to tell you why it doesn't satisfy the time synch requirement. Scott Rohling On Wed, Mar 18, 2015 at 1:00 PM, Vitale, Joseph joseph.vit...@bnymellon.com wrote: Using STP to set clock for zVM LPAR. zVM and zLinux guest show time, both in sync. Trying to avoid setting up NTPD and starting on all zLinux if not necessary. Came about due to checks comparing zLinux software configuration vs X86 configuration, they run NTPD. So, I was asked to do same. Never seen an issue with time under zLinux. Thank you for your assistance Joe Joseph Vitale Technology Services Group Mainframe Operating Systems Pershing Plaza 95 Christopher Columbus Drive Floor 14 Jersey City, N.J. 07302 Work 201-395-1509 Cell917-903-0102 -Original Message- From: Linux on 390 Port [mailto:LINUX-390@VM.MARIST.EDU] On Behalf Of Rob van der Heij Sent: Wednesday, March 18, 2015 3:54 PM To: LINUX-390@VM.MARIST.EDU Subject: Re: Network Time Protocol Daemon needed for zLinux? On 18 March 2015 at 20:04, Vitale, Joseph joseph.vit...@bnymellon.com wrote: My Linux runs under zVM, not in a stand alone LPAR. So, NTP or STP not required, correct ? That depends on whether you have STP steer the clock for the LPARs. It's a priced feature. If Q TIME on z/VM is now very accurate, then you're most likely steering and your Linux guests will follow. When z/VM is not running on time, then all Linux guests will get a clock (the same) that is slightly off as well. If that bothers you (your applications rather) then you can either implement STP or have each guest synchronize it's won clock with ntpd etc. If you frequently reboot, then ntpdate during startup might be enough to stay somewhat on time (eg 3 seconds per week). Some things like Kerberos expect you to be sort-of on time (10's of seconds, iirc). My experience is that the quality of the clock with ntpd is somewhat less, but that's a moot point when it's your only option. Yes, it's true that running ntpd takes resources. But much middleware does too and we're not on G3 anymore. PS Yes, I did do an ntpq for CMS a while back, but the year does not have nearly enough Friday nights to come up with an alternative for STP. Rob -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/ The information contained in this e-mail, and any attachment, is confidential and is intended solely for the use of the intended recipient. Access, copying or re-use of the e-mail or any attachment, or any information contained therein, by any other person is not authorized. If you are not the intended recipient please return the e-mail to the sender and delete it from your computer. Although we attempt to sweep e-mail and attachments for viruses, we do not guarantee that either are virus-free and accept no liability for any damage sustained as a result of viruses. Please refer to http://disclaimer.bnymellon.com/eu.htm for certain disclosures relating to European legal entities. -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/ -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: Network Time Protocol Daemon needed for zLinux?
On 18 March 2015 at 23:02, Scott Rohling scott.rohl...@gmail.com wrote: Not sure how strongly you were asked :) -- but I would explain that z/VM-Linux are already synced with whatever NTP server the z is using.. and I would ask why it should then be necessary. Put the burden of explanation on them to tell you why it doesn't satisfy the time synch requirement. Scott Rohling Such is life. I remember a discussion with the Linux admin that went like this :-) R: You're running ntpd - you shouldn't when the hypervisor is already synchronized A: But I need the exact time, and that requires ntpd R: No, it does not. It's wasting resources and does not do you any good. A: I need it anyway, for exact time. R: Your time on z/Linux will be less exact with ntpd than without A: I does not have to be that exact, so I will run ntpd anyway -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: Network Time Protocol Daemon needed for zLinux?
I don't think anybody will answer that question :-)That depends on what your requirements are.. are you communicating with a non-z database for example where time synching must be assured? Are they actually in the same stratum as the other platform servers? What requirement are you trying to satisfy here? Scott Rohling On Wed, Mar 18, 2015 at 12:04 PM, Vitale, Joseph joseph.vit...@bnymellon.com wrote: My Linux runs under zVM, not in a stand alone LPAR. So, NTP or STP not required, correct ? Thanks Joseph Vitale Technology Services Group Mainframe Operating Systems Pershing Plaza 95 Christopher Columbus Drive Floor 14 Jersey City, N.J. 07302 Work 201-395-1509 Cell917-903-0102 -Original Message- From: Linux on 390 Port [mailto:LINUX-390@VM.MARIST.EDU] On Behalf Of Rob van der Heij Sent: Wednesday, March 18, 2015 2:53 PM To: LINUX-390@VM.MARIST.EDU Subject: Re: Network Time Protocol Daemon needed for zLinux? Just a warning: my understanding is that this quote is talking about Linux in LPAR; that z/VM does not virtualize the ETR/STP. For the rest of us: When you have STP steer the LPAR TOD to keep z/VM on time, Linux will inherit the same (UTC) TOD and runs better on time than anything you can do with ntpd. This will cover the leap second in that the TOD appears to slow down for a few hours, to be on time in the morning. On 18 March 2015 at 19:33, John McKown john.archie.mck...@gmail.com wrote: On Wed, Mar 18, 2015 at 10:46 AM, Vitale, Joseph joseph.vit...@bnymellon.com wrote: Hello, Currently not running NTPD under RedHat, is that necessary or does zVM present time adjustment via Sysplex Timer? I think this answers that question: http://www-01.ibm.com/support/knowledgecenter/linuxonibm/com.ibm.linux .z.lgdd/lgdd_r_feature_time.html quote ETR- and STP-based clock synchronization Your Linux instance might be part of an extended remote copy (XRC) setup that requires synchronization of the Linux time-of-day (TOD) clock with a timing network. Linux on z Systems supports external time reference (ETR) and system time protocol (STP) based TOD synchronization. ETR and STP work independently of one another. If both ETR and STP are enabled, Linux might use either to synchronize the clock. For more information about ETR, see the IBM(r) Redbooks(r) technote at www.ibm.com/redbooks/abstracts/tips0217.html For information about STP, see www.ibm.com/systems/z/advantages/pso/stp.html Both ETR and STP support are included in the Linux kernel. No special build options are required. ETR requires at least one ETR unit that is connected to an external time source. For availability reasons, many installations use a second ETR unit. The ETR units correspond to two ETR ports on Linux. Always set both ports online if two ETR units are available. Attention: Be sure that a reliable timing signal is available before enabling clock synchronization. With enabled clock synchronization, Linux expects regular timing signals and might stop indefinitely to wait for such signals if it does not receive them. Enabling clock synchronization when booting Use kernel parameters to enable clock synchronization when booting. Enabling and disabling clock synchronization You can use the sysfs interfaces of ETR and STP to enable and disable clock synchronization on a running Linux instance. Parent topic: System resources /quote Thanks Joe -- If you sent twitter messages while exploring, are you on a textpedition? He's about as useful as a wax frying pan. 10 to the 12th power microphones = 1 Megaphone Maranatha! John McKown -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/ -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/ The information contained in this e-mail, and any attachment, is confidential and is intended solely for the use of the intended recipient. Access, copying or re-use of the e-mail or any attachment, or any information contained therein, by any other person is not authorized. If you are not the intended recipient please return the e-mail to the sender and delete it from your computer. Although we
Re: Network Time Protocol Daemon needed for zLinux?
On 18 March 2015 at 20:04, Vitale, Joseph joseph.vit...@bnymellon.com wrote: My Linux runs under zVM, not in a stand alone LPAR. So, NTP or STP not required, correct ? That depends on whether you have STP steer the clock for the LPARs. It's a priced feature. If Q TIME on z/VM is now very accurate, then you're most likely steering and your Linux guests will follow. When z/VM is not running on time, then all Linux guests will get a clock (the same) that is slightly off as well. If that bothers you (your applications rather) then you can either implement STP or have each guest synchronize it's won clock with ntpd etc. If you frequently reboot, then ntpdate during startup might be enough to stay somewhat on time (eg 3 seconds per week). Some things like Kerberos expect you to be sort-of on time (10's of seconds, iirc). My experience is that the quality of the clock with ntpd is somewhat less, but that's a moot point when it's your only option. Yes, it's true that running ntpd takes resources. But much middleware does too and we're not on G3 anymore. PS Yes, I did do an ntpq for CMS a while back, but the year does not have nearly enough Friday nights to come up with an alternative for STP. Rob -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
Re: Network Time Protocol Daemon needed for zLinux?
We run NTP on all the Linux guests under zVM (and we have STP for VM). There were just too many things that require it and it wasn't worth the effort to make them believe that it wasn't necessary. -Original Message- From: Linux on 390 Port [mailto:LINUX-390@VM.MARIST.EDU] On Behalf Of Vitale, Joseph Sent: Wednesday, March 18, 2015 1:00 PM To: LINUX-390@VM.MARIST.EDU Subject: Re: [LINUX-390] Network Time Protocol Daemon needed for zLinux? Using STP to set clock for zVM LPAR. zVM and zLinux guest show time, both in sync. Trying to avoid setting up NTPD and starting on all zLinux if not necessary. Came about due to checks comparing zLinux software configuration vs X86 configuration, they run NTPD. So, I was asked to do same. Never seen an issue with time under zLinux. Thank you for your assistance Joe Joseph Vitale Technology Services Group Mainframe Operating Systems Pershing Plaza 95 Christopher Columbus Drive Floor 14 Jersey City, N.J. 07302 Work 201-395-1509 Cell917-903-0102 -Original Message- From: Linux on 390 Port [mailto:LINUX-390@VM.MARIST.EDU] On Behalf Of Rob van der Heij Sent: Wednesday, March 18, 2015 3:54 PM To: LINUX-390@VM.MARIST.EDU Subject: Re: Network Time Protocol Daemon needed for zLinux? On 18 March 2015 at 20:04, Vitale, Joseph joseph.vit...@bnymellon.com wrote: My Linux runs under zVM, not in a stand alone LPAR. So, NTP or STP not required, correct ? That depends on whether you have STP steer the clock for the LPARs. It's a priced feature. If Q TIME on z/VM is now very accurate, then you're most likely steering and your Linux guests will follow. When z/VM is not running on time, then all Linux guests will get a clock (the same) that is slightly off as well. If that bothers you (your applications rather) then you can either implement STP or have each guest synchronize it's won clock with ntpd etc. If you frequently reboot, then ntpdate during startup might be enough to stay somewhat on time (eg 3 seconds per week). Some things like Kerberos expect you to be sort-of on time (10's of seconds, iirc). My experience is that the quality of the clock with ntpd is somewhat less, but that's a moot point when it's your only option. Yes, it's true that running ntpd takes resources. But much middleware does too and we're not on G3 anymore. PS Yes, I did do an ntpq for CMS a while back, but the year does not have nearly enough Friday nights to come up with an alternative for STP. Rob -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/ The information contained in this e-mail, and any attachment, is confidential and is intended solely for the use of the intended recipient. Access, copying or re-use of the e-mail or any attachment, or any information contained therein, by any other person is not authorized. If you are not the intended recipient please return the e-mail to the sender and delete it from your computer. Although we attempt to sweep e-mail and attachments for viruses, we do not guarantee that either are virus-free and accept no liability for any damage sustained as a result of viruses. Please refer to http://disclaimer.bnymellon.com/eu.htm for certain disclosures relating to European legal entities. -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/ -- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For more information on Linux on System z, visit http://wiki.linuxvm.org/
