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Mike Purcell
Asked: 2014-01-12 12:26:55 +0800 CST

NTP stopped working after update to CentOS 6.5

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A few days ago I had ntp setup on my network, and everything was running fine. One node was set to sync with upstream servers, and the rest of the nodes from the one set to sync upstream.

Yesterday I updated from CentOS 6.4 -> 6.5 and now all of the ntp functionality has ceased to operate as expected.

In efforts of trying to debug the situation, I ran the following on the upstream server:

$ -> ntpq -pnd
::1: timed out, nothing received
***Request timed out

$ -> ntpq -4 -pnd
1 packets reassembled into response
remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
2 packets reassembled into response
*50.116.55.65    64.246.132.14    2 u   42   64   37   77.742  189.392  14.812
2 packets reassembled into response
 199.102.46.73   .GPS.            1 u   44   64   37   73.786  216.082  18.406
2 packets reassembled into response
 198.60.22.240   .GPS.            1 u   48   64   37   22.617  189.405  15.996
2 packets reassembled into response
 127.127.1.0     .LOCL.          10 l  306   64   20    0.000    0.000   0.000

I get the same results (save for diff ip) on the nodes. It seems, somehow the ntp service is defaulting to ipv6, which I do not have configured. I've read some sites saying to pass -4 to the ntpd service, but how would I do that using chkconfig? Some other readings indicated that I should disable ipv6 via the kernel, but this seems like overkill.

Any suggestions?

For the sake of completeness, adding config file:

driftfile /var/lib/ntp/drift

# Permit time synchronization with our time source, but do not
# permit the source to query or modify the service on this system.
restrict default kod nomodify notrap nopeer noquery
restrict -6 default kod nomodify notrap nopeer noquery

# Permit all access over the loopback interface.  This could
# be tightened as well, but to do so would effect some of
# the administrative functions.
restrict 127.0.0.1

restrict 10.0.0.0 mask 255.255.192.0 nomodify notrap


server 0.centos.pool.ntp.org iburst

server 1.centos.pool.ntp.org

server 2.centos.pool.ntp.org


# In case net access is temporarily down
server 127.127.1.0
fudge 127.127.1.0 stratum 10
linux

1 Answers

  1. Best Answer

    Since it's trying to use IPv6 you probably want to allow it in your config file:

    restrict -6 ::1
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