[ntp:questions] Re: Linux NTP server problems serving time.

Steve Kostecke kostecke at ntp.isc.org
Sat Jul 16 03:48:57 UTC 2005


On 2005-07-15, Peter Stickney <peter at peterstickney.com> wrote:

> OK, Ive got kernel 2.6.9,

There are some known issues with NTP, 2.6.x Linux kernels, and some
motherboards.

Some 2.6.x kernels are compiled with a HZ setting of 1000, instead of
100, which leads to clock instability.

You may need to set clock=tsc or disable the APIC (using kernel boot
args) to get a stable clock.

You may need to tweak your IDE disk parameters to prevent lost
interrupts.

See http://ntp.isc.org/bin/view/Support/KnownHardwareIssues and
http://ntp.isc.org/bin/view/Support/KnownOsIssues

> slackware 10.0. ntpd 4.2.0. This one box is the NTP server for a small
> ( 60 ) Win2000 network with 5 more linux servers also getting their
> time from this one box. The issue looks like the box doesnt want to
> sync to pool.ntp.org

Depending on your application, you may want to consider using known time
servers instead of random pool servers.

You should consider whether or not having a single point of failure
(i.e. one LAN time server) is acceptable. You may find the information
at http://ntp.isc.org/bin/view/Support/DesigningYourNTPNetwork helpful.

> servers with the daemon. BUT. If I run 'ntpdate pool.ntp.org' it syncs
> fine. As a result, none of the clients will sync with this one because
> they know it's off. Windows says "The NTP server isn't sync'd, time
> not set."

The first step is to get your LAN time server synchronized and stable.

Here's an ntp.conf:

------------------------------------8X------------------------------------

# General Settings
driftfile /etc/ntp.drift
logfile /var/log/ntp.log

# Statistics
# Uncomment the following lines (and create the statsdir) to activate
# statsdir /var/log/ntpstats/
# statistics loopstats peerstats clockstats
# filegen loopstats file loopstats type day enable
# filegen peerstats file peerstats type day enable
# filegen clockstats file clockstats type day enable

# Default Restriction
# See http://ntp.isc.org/Support/AccessRestrictions for more information
restrict default nomodify nopeer notrap
restrict 127.0.0.1

# LocalCLK
# This will allow your ntpd to continue to serve time when it's not
# synchronized to a real time source. 
server 127.127.1.0
fudge  127.127.1.0 stratum 10

# Time Servers
# See http://ntp.isc.org/Servers for the public time server lists
server us.pool.ntp.org iburst
server us.pool.ntp.org iburst
server us.pool.ntp.org iburst
server us.pool.ntp.org iburst
server us.pool.ntp.org iburst

------------------------------------8X------------------------------------

One you get this going please post the output of 'ntpq -pcrv'.

> 12 Jul 20:00:13 ntpd[25341]: synchronized to 69.44.57.60, stratum=3
> 12 Jul 20:15:47 ntpd[25341]: time reset +3.526547 s

Drifting 3.5 seconds in 15 minutes is not a good sign. You need to get
this drifting under control before that system will be able to serve
time.

What does this system do aside from serving time? Is it heavily loaded?

-- 
Steve Kostecke <kostecke at ntp.isc.org>
NTP Public Services Project - http://ntp.isc.org/




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