Ntp Service
Linux
Documentation
- detailed client server configuration http://www.thegeekstuff.com/2014/06/linux-ntp-server-client
- less detailed client server configuration https://www.linuxsolutions.org/faqs/generic/ntpserver
- ntpq http://osr507doc.xinuos.com/en/man/html.ADMN/ntpq.ADMN.html
Server
- with the same service "ntpd" in linux you can do client and server
- you need to have the ntp service installed and running and inside the ntp server and client
- the main difference (not the only one) is that in the server it points to an external one in the client instead point to the server private dns/ip
- in the servers firewall don't forget to open the port udp/123 to receive the call
Verification
client machine with a NEVER working ntp server
~> ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
ip-172-29-1-209 .INIT. 16 u - 64 0 0.000 0.000 0.000
the same machine after that you fixed the problem
~> ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
*ip-172-29-1-209 52.17.30.119 3 u 39 64 3 0.687 -9.021 4.911
if the server doesn't respond anymore you will notice that the when number is higher than the poll number
~> ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
*ip-172-29-1-209 193.104.228.123 3 u 96 64 376 0.627 4.330 1.301
information about the ntpq -p command
peers
Obtains a list of in-spec peers of the server, along with a summary of each peer's state. Summary information includes:
the address of the remote peer
the reference ID (0.0.0.0 if the reference ID is unknown)
the stratum of the remote peer
the type of the peer (local, unicast, multicast or broadcast)
when the last packet was received
the polling interval, in seconds
the reachability register, in octal
the current estimated delay, offset and dispersion of the peer, all in seconds
The character in the left margin indicates the fate of this peer in the clock selection process. The codes mean:
<sp>
discarded due to high stratum and/or failed sanity checks
x
designated falsticker by the intersection algorithm
.
culled from the end of the candidate list
-
discarded by the clustering algorithm
+
included in the final selection set
#
selected for synchronization but distance exceeds maximum
*
selected for synchronization
o
selected for synchronization, PPS signal in use
Note that since the peers command depends on the ability to parse the values in the responses it gets, it may fail to work from time to time with servers which poorly control the data formats.
The contents of the host field may be one of four forms:
a host name
an IP address
a reference clock implementation name with its parameter
REFCLK(implementation_number, parameter)
On hostnames no only IP addresses will be displayed.
Multiple servers
in this example you can see after a while the not working server ip-172-29-1-169 is not anymore the selected one
~> ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
ip-172-29-1-209 .INIT. 16 u - 256 0 0.000 0.000 0.000
+ip-172-29-1-226 52.209.118.149 3 u 17 64 377 0.596 -12.311 3.963
*ip-172-29-1-169 193.1.219.116 2 u 86 64 376 0.660 -6.848 7.641
~> ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
ip-172-29-1-209 .INIT. 16 u - 1024 0 0.000 0.000 0.000
*ip-172-29-1-226 52.209.118.149 3 u 74 128 377 0.644 3.143 2.923
ip-172-29-1-169 193.1.219.116 2 u 1512 64 0 1.052 -10.690 0.000
Windows 7
Utilissima pagina con tool per windows 7 e xp che non hanno la possibilità impostare il server ntp propriamente
http://www.inrim.it/ntp/howtosync_i.shtml
pool.ntp.org è sempre un servizio accettabile
versione della pagina: 6, ultima modifica: 21 Jun 2017 14:41