Linux – Setting up an NTP server for the LAN

linuxntpd

I am trying to setup my Debian 6 (Squeeze) VM to act as a local time server for my network. I have it set to sync with tock.usno.navy.mil which is a stratum 1 server.

I am having some problems finding any information on how to setup the ntp daemon to serve the time to clients requesting the time. I have looked through the ntpd man page and that was probably the best doc I found. support.ntp.org was pretty much useless to me, the documentation I found was talking more about how NTP works not how to configure a server.

I also noticed I am not getting anything in my logs about being synced with the server that I am listed.

Any help anyone can offer would be great, I am not sure what is wrong. I am sure it is something I am doing. I had a previous time server running but my SAN blew up and I was not making backups since it was for testing. So I have no old config to look at.

Here is a copy of ntp.conf since there is nothing in here that has a any personal information I thought posting might help.

# /etc/ntp.conf, configuration for ntpd; see ntp.conf(5) for help

driftfile /var/lib/ntp/ntp.drift


# Enable this if you want statistics to be logged.
#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


# You do need to talk to an NTP server or two (or three).
#server ntp.your-provider.example

# pool.ntp.org maps to about 1000 low-stratum NTP servers.  Your server will
# pick a different set every time it starts up.  Please consider joining the
# pool: <http://www.pool.ntp.org/join.html>
server tock.usno.navy.mil iburst


# Access control configuration; see /usr/share/doc/ntp-doc/html/accopt.html for
# details.  The web page <http://support.ntp.org/bin/view/Support/AccessRestrictions>
# might also be helpful.
#
# Note that "restrict" applies to both servers and clients, so a configuration
# that might be intended to block requests from certain clients could also end
# up blocking replies from your own upstream servers.

# By default, exchange time with everybody, but don't allow configuration.
restrict -4 default kod notrap nomodify nopeer noquery
restrict -6 default kod notrap nomodify nopeer noquery
restrict 10.0.0.0 mask 255.255.255.0 notrap nomodify

# Local users may interrogate the ntp server more closely.
restrict 127.0.0.1
restrict ::1

# Clients from this (example!) subnet have unlimited access, but only if
# cryptographically authenticated.
#restrict 192.168.123.0 mask 255.255.255.0 notrust


# If you want to provide time to your local subnet, change the next line.
# (Again, the address is an example only.)
#broadcast 192.168.123.255

# If you want to listen to time broadcasts on your local subnet, de-comment the
# next lines.  Please do this only if you trust everybody on the network!
#disable auth
#broadcastclient

Here the output from ntpq -p

root@ns01:/home/ns01# ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 ntp1.usno.navy. .USNO.           1 u   43   64    1   34.747  -2891.0 1669.51

Output from iptables

Output from `iptables -L -n -v`

Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination

Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination

Update

When I remove the line restrict 10.0.0.0 mask 255.255.255.0 notrap nomodify from my config ntp seems to spring to life. This is what I see now when I look at ntpq -p

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
-barricade.rack9 209.51.161.238   2 u   39   64  377   37.887  -2977.7   3.180
*gallifrey.chpc. 92.113.67.127    2 u   26   64  377   68.155  -2969.0   3.024
+clock.trit.net  204.34.198.41    2 u    2   64  377   83.146  -2972.0   3.756
+ntp1.Housing.Be 169.229.128.214  3 u   63   64  377  105.803  -2972.6   2.698

Test Desktop ifconfig output (requested by MadHatter)

eth0      Link encap:Ethernet  HWaddr 08:00:27:59:2d:3a  
          inet addr:10.0.0.21  Bcast:10.0.0.255  Mask:255.255.255.0
          inet6 addr: fe80::a00:27ff:fe59:2d3a/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:62103 errors:0 dropped:0 overruns:0 frame:0
          TX packets:51822 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:10339609 (9.8 MiB)  TX bytes:7249927 (6.9 MiB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:56 errors:0 dropped:0 overruns:0 frame:0
          TX packets:56 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:5066 (4.9 KiB)  TX bytes:5066 (4.9 KiB)

Best Answer

You need to insure that udp port 123 is open inbound to your server from your LAN and back out to your LAN from your server.

Also, you can check the status of your server's sync by running

"ntpq -p"

I'd recommend adding at least three upstream servers to your config.

Try pointing one of your clients to your server via "ntpdate servername" and see what happens.

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