FAQ Search Today's Posts Mark Forums Read
» Video Reviews

» Linux Archive

Linux-archive is a website aiming to archive linux email lists and to make them easily accessible for linux users/developers.


» Sponsor

» Partners

» Sponsor

Go Back   Linux Archive > ArchLinux > ArchLinux General Discussion

 
 
LinkBack Thread Tools
 
Old 07-02-2012, 06:30 PM
"David C. Rankin"
 
Default Leap seconds ntp and chrony?

On 07/02/2012 12:13 PM, Jelle van der Waa wrote:

On 02/07/12 19:09, mike cloaked wrote:

>There has been a fair amount of disruption to systems over a
>widespread geographic area due to the mutex leap second bug from
>midnight Saturday, and from what I read this was triggered by ntpd
>calling specific routines from the kernel - does anyone know if the
>same bug has also hit systems using chrony if that was in use instead
>of ntp?
>
>I guess that the kernel patches being written by John Stulz at
>https://lkml.org/lkml/2012/7/1/203 will filter through to a kernel
>update at some point?
>

If you don't have problems now, you don't even need to worry. Else just
reboot


The biggest problems I saw were with java based apps. I was running a couple
of minecraft servers for my kids and as soon as the leap second was inserted:


/var/log/kernel.log.1:Jun 30 18:59:59 archangel kernel: [268959.468848] Clock:
inserting leap second 23:59:60 UTC


minecraft servers on both boxes errored out with "Has system time changed --
unable to keep up" errors. Simply stopping and starting the applications was
_not_ enough, it required a complete reboot of the system before
minecraft_server in particular would run again.


I wondered how widespread the disruption would be, but just judging from my 2
boxes -- I knew it would be fairly widespread.


My setup was with dcron and ntp.


--
David C. Rankin, J.D.,P.E.
 
Old 07-02-2012, 10:56 PM
Kevin Chadwick
 
Default Leap seconds ntp and chrony?

> My setup was with dcron and ntp.

Considering servers don't get chance to run the RTC battery down. I've
never understood why everyone uses NTP which is an unneeded
security risk anyway (OpenBSDs ain't bad). Do we think, in 1938-1945 men
couldn't synchronise watches without NTP? Saves checking I suppose but
that's it or does it?

--
__________________________________________________ ______

Why not do something good every day and install BOINC.
__________________________________________________ ______
 
Old 07-02-2012, 10:58 PM
Kevin Chadwick
 
Default Leap seconds ntp and chrony?

> > My setup was with dcron and ntp.
>
> Considering servers don't get chance to run the RTC battery down. I've
> never understood why everyone uses NTP which is an unneeded
> security risk anyway (OpenBSDs ain't bad). Do we think, in 1938-1945 men
> couldn't synchronise watches without NTP? Saves checking I suppose but
> that's it or does it?
>

I accept there are some dodgy RTCs or perhaps old unreliable ones but
do you run NTP or replace the server?

--
__________________________________________________ ______

Why not do something good every day and install BOINC.
__________________________________________________ ______
 
Old 07-02-2012, 11:37 PM
Mauro Santos
 
Default Leap seconds ntp and chrony?

On 02-07-2012 23:58, Kevin Chadwick wrote:
>>> My setup was with dcron and ntp.
>>
>> Considering servers don't get chance to run the RTC battery down. I've
>> never understood why everyone uses NTP which is an unneeded
>> security risk anyway (OpenBSDs ain't bad). Do we think, in 1938-1945 men
>> couldn't synchronise watches without NTP? Saves checking I suppose but
>> that's it or does it?
>>
>
> I accept there are some dodgy RTCs or perhaps old unreliable ones but
> do you run NTP or replace the server?
>

I'm not sure that the RTC, even in servers, is made to be very stable
with temperature changes and aging, it sure isn't for consumer hardware.

Google does run ntp on their network to keep all the machines in sync,
otherwise stuff stops working, so i guess ntp is not that evil or at
least it has its uses.

--
Mauro Santos
 
Old 07-02-2012, 11:49 PM
Karol Blazewicz
 
Default Leap seconds ntp and chrony?

On Tue, Jul 3, 2012 at 1:37 AM, Mauro Santos <registo.mailling@gmail.com> wrote:
> Google does run ntp on their network to keep all the machines in sync,
> otherwise stuff stops working, so i guess ntp is not that evil or at
> least it has its uses.

http://www.h-online.com/open/news/item/Leap-second-Linux-can-freeze-1629805.html
In view of the recurring leap second disruptions in its own server
farms, Google took the motto "prevention is better than cure" to heart
and established a "leap smear" process: using modified NTP servers,
Google ensures that every NTP update on the day of the leap second
inserts a few milliseconds that add up to a second by the time the
leap second is actually inserted. Such minor system time differences
are usually tolerated by operating systems.
 
Old 07-03-2012, 01:37 AM
Damjan
 
Default Leap seconds ntp and chrony?

My setup was with dcron and ntp.


Considering servers don't get chance to run the RTC battery down. I've
never understood why everyone uses NTP


RTC is only read on boot-up on all Linux systems. And from what I've
seen they are fairly inaccurate.


Otherwise, the Linux kernel counts its own time in software, but that
time could drift very easily too.





--
дамјан
 
Old 07-03-2012, 07:40 AM
"P .NIKOLIC"
 
Default Leap seconds ntp and chrony?

On Mon, 2 Jul 2012 23:58:24 +0100
Kevin Chadwick <ma1l1ists@yahoo.co.uk> wrote:

> > > My setup was with dcron and ntp.
> >
> > Considering servers don't get chance to run the RTC battery down.
> > I've never understood why everyone uses NTP which is an unneeded
> > security risk anyway (OpenBSDs ain't bad). Do we think, in
> > 1938-1945 men couldn't synchronise watches without NTP? Saves
> > checking I suppose but that's it or does it?
> >
>
> I accept there are some dodgy RTCs or perhaps old unreliable ones but
> do you run NTP or replace the server?
>

It's very simple Run NTP .

Is your system of national importance NO do you have top secret
millitary info on your system NO , So what is with this continual
whimpering about security risks that are almost non existant

Pete .


--
Linux 7-of-9 3.4.4-2-ARCH #1 SMP PREEMPT Sun Jun 24 18:59:47 CEST 2012
x86_64 GNU/Linux
 
Old 07-03-2012, 11:07 AM
Kevin Chadwick
 
Default Leap seconds ntp and chrony?

> it sure isn't for consumer hardware.

They could use better use of crystals in the main like watches but I
think they are good enough for all except corner cases. One guy on the
android list said research had come out with an average of two second
slide sqew per week or something rediculous and which I don't believe
for one second. I'll start my own tests sometime and find out, including
software slide. Either way NTP is irrelevent to me, my servers seem in
sync too. So I'd still say the best solution for most purposes is not
to use NTP at all.

--
__________________________________________________ ______

Why not do something good every day and install BOINC.
__________________________________________________ ______
 
Old 07-03-2012, 01:10 PM
Mauro Santos
 
Default Leap seconds ntp and chrony?

On 03-07-2012 12:07, Kevin Chadwick wrote:
>> it sure isn't for consumer hardware.
>
> They could use better use of crystals in the main like watches but I
> think they are good enough for all except corner cases. One guy on the
> android list said research had come out with an average of two second
> slide sqew per week or something rediculous and which I don't believe
> for one second. I'll start my own tests sometime and find out, including
> software slide. Either way NTP is irrelevent to me, my servers seem in
> sync too. So I'd still say the best solution for most purposes is not
> to use NTP at all.
>

The problem is that the crystal isn't the only thing that affects the
stability of a clock. Without looking at it in-depth I would dare say
that the crystal is what contributes less to instabilities. I would say
that temperature and voltage dependencies, manufacturing process
variations and noise immunity in the RTC electronics might account for
more variation than the variation that comes from the crystals.

Better electronics and means a more complex circuit thus more silicon
area and cost per chip, a more complex circuit probably means more power
usage thus it will drain backup batteries or capacitors faster, so
unless there is a strong requirement for it there is no incentive to use
really circuits with an higher accuracy or better drift characteristics
or to provide good supply voltage filtering and implement EMI shielding,
all these things add to cost and the area/volume required on the PCB.

For most usages the RTC is accurate enough, when more precision is
desired you either source parts that specifically comply with your
requirements or you can always use some ntp client to sync from a time
server, you most probably have to use some ntp client to sync from a
time server when you have more than one machine running and want to have
consistent time stamps between machines.

Like everything else ntpd has to be properly secured and configured, if
properly done I suppose it isn't a bigger security problem than anything
else with network access. This problem about the leap second and
programs going awry is due to a bug in the kernel and not a problem with
ntp itself, the only fault that can be attributed to ntp is to expose
that bug.

--
Mauro Santos
 
Old 07-03-2012, 01:53 PM
Leonid Isaev
 
Default Leap seconds ntp and chrony?

On Tue, 03 Jul 2012 14:10:55 +0100
Mauro Santos <registo.mailling@gmail.com> wrote:

> On 03-07-2012 12:07, Kevin Chadwick wrote:
> >> it sure isn't for consumer hardware.
> >
> > They could use better use of crystals in the main like watches but I
> > think they are good enough for all except corner cases. One guy on the
> > android list said research had come out with an average of two second
> > slide sqew per week or something rediculous and which I don't believe
> > for one second. I'll start my own tests sometime and find out, including
> > software slide. Either way NTP is irrelevent to me, my servers seem in
> > sync too. So I'd still say the best solution for most purposes is not
> > to use NTP at all.
> >
>
> The problem is that the crystal isn't the only thing that affects the
> stability of a clock. Without looking at it in-depth I would dare say
> that the crystal is what contributes less to instabilities. I would say
> that temperature and voltage dependencies, manufacturing process
> variations and noise immunity in the RTC electronics might account for
> more variation than the variation that comes from the crystals.
>
> Better electronics and means a more complex circuit thus more silicon
> area and cost per chip, a more complex circuit probably means more power
> usage thus it will drain backup batteries or capacitors faster, so
> unless there is a strong requirement for it there is no incentive to use
> really circuits with an higher accuracy or better drift characteristics
> or to provide good supply voltage filtering and implement EMI shielding,
> all these things add to cost and the area/volume required on the PCB.
>
> For most usages the RTC is accurate enough, when more precision is
> desired you either source parts that specifically comply with your
> requirements or you can always use some ntp client to sync from a time
> server, you most probably have to use some ntp client to sync from a
> time server when you have more than one machine running and want to have
> consistent time stamps between machines.

RTC was never designed to be precise. These days OS kernels use ~ 10
nanosecond resolution, so RTC are not fit for the job simply because they run
from battery which looses charge over time. A proper use for RTC is as a
reference point to start off your kernel time.

Besides, most modern devices (routers, cable modems, ARM/MIPS-based PC) do not
even have an RTC -- they start from Jan 1 1970 and then sync clock over web.

>
> Like everything else ntpd has to be properly secured and configured, if
> properly done I suppose it isn't a bigger security problem than anything
> else with network access. This problem about the leap second and
> programs going awry is due to a bug in the kernel and not a problem with
> ntp itself, the only fault that can be attributed to ntp is to expose
> that bug.
>

Exactly. Also, ntp doesn't even use TCP -- all ports involved are UDP.

--
Leonid Isaev
GnuPG key: 0x164B5A6D
Fingerprint: C0DF 20D0 C075 C3F1 E1BE 775A A7AE F6CB 164B 5A6D
 

Thread Tools




All times are GMT. The time now is 01:23 AM.

VBulletin, Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Relevant URLs by vBSEO ©2007, Crawlability, Inc.
Copyright 2007 - 2008, www.linux-archive.org