ntp: why am I not in sync with the rest of the world?

stateless · 05-14-2014, 12:07 PM

Hi. I am simply trying to configure a Debian workstation to have accurate time via ntp. I installed ntp, and kept it using the default config file (with debian ntp pool). But I am confused: the values returned by both the "date" command and "ntptime" are about three minutes different from my local university time, as well as the time displayed on several time display Web sites I've visited (which all agree with the university time). I tried switching from debian pool to the university ntp server, but no change. Please advise.

Code:

# ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 host2.kingrst.c .INIT.          16 u    -  128    0    0.000    0.000   0.000
 162.250.145.46  .INIT.          16 u    -  128    0    0.000    0.000   0.000
 2607:fcd0:daaa: .INIT.          16 u    -  128    0    0.000    0.000   0.000
 lani.12.am      .INIT.          16 u    -  128    0    0.000    0.000   0.000
# ntptime
ntp_gettime() returns code 0 (OK)
  time d71e20d4.c298d000  Wed, May 14 2014  9:05:24.760, (.760144),
  maximum error 329016 us, estimated error 16 us, TAI offset 0
ntp_adjtime() returns code 0 (OK)
  modes 0x0 (),
  offset 0.000 us, frequency 0.000 ppm, interval 1 s,
  maximum error 329016 us, estimated error 16 us,
  status 0x1 (PLL),
  time constant 7, precision 1.000 us, tolerance 500 ppm,

smallpond · 05-14-2014, 12:41 PM

Looks like ntpd can't reach the servers: INIT state and all fields 0. Maybe firewall is blocking? grep the logs for ntpd.

stateless · 05-14-2014, 01:03 PM

Here's the syslog:

Code:

root@<snip>:~# grep ntp /var/log/syslog
May 14 08:54:26 <snip> ntpd[12024]: ntpd 4.2.6p5@1.2349-o Sat May 12 09:54:55 UTC 2012 (1)
May 14 08:54:26 <snip> ntpd[12025]: proto: precision = 0.100 usec
May 14 08:54:26 <snip> ntpd[12025]: Listen and drop on 0 v4wildcard 0.0.0.0 UDP 123
May 14 08:54:26 <snip> ntpd[12025]: Listen and drop on 1 v6wildcard :: UDP 123
May 14 08:54:26 <snip> ntpd[12025]: Listen normally on 2 lo 127.0.0.1 UDP 123
May 14 08:54:26 <snip> ntpd[12025]: Listen normally on 3 eth0 <snip> UDP 123
May 14 08:54:26 <snip> ntpd[12025]: Listen normally on 4 eth0 <snip> UDP 123
May 14 08:54:26 <snip> ntpd[12025]: Listen normally on 5 eth0 <snip> UDP 123
May 14 08:54:26 <snip> ntpd[12025]: Listen normally on 6 lo ::1 UDP 123
May 14 08:54:26 <snip> ntpd[12025]: peers refreshed
May 14 08:54:26 <snip> ntpd[12025]: Listening on routing socket on fd #23 for interface updates

I don't have to have any ports open into my workstation, right? (Just outgoing connections?)

Code:

# iptables -S
-P INPUT DROP
-P FORWARD ACCEPT
-P OUTPUT ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -p tcp -m tcp --dport 22 -j ACCEPT
-A INPUT -p icmp -j ACCEPT

It seems quite plausible there could be a firewall problem in my department's network configuration. I'll check into this.

smallpond · 05-14-2014, 01:56 PM

Unless you configured something very oddly then there are no connections in ntp. It runs on UDP port 123 and is bidirectional, so must be open for sending and receiving packets.

stateless · 05-14-2014, 03:03 PM

I opened up the udp port, but this didn't seem to be enough. So I did a little more research, and it looks like it was a firewall issue. Found out we had our own local ntp server, and that one seems to work fine for me.