Ntp

Serveur NTP

on commence par installer les paquets ntp :

sudo apt-get install ntp

puis on modifie le fichier /etc/ntp.conf

# /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

listen on *

# You do need to talk to an NTP server or two (or three).
server ntp.ubuntu.com prefer
server ntp2.jussieu.fr
server ntp.uvsq.fr
server 0.fr.pool.ntp.org

# Access control configuration; see /usr/share/doc/ntp-doc/html/accopt.html for
# details. The web page 
# 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 

# Local users may interrogate the ntp server more closely.
restrict 127.0.0.1 nomodify
# On permet aux machines du réseau 192.168.10.0/24 d’intérroger le serveur NTP
restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap
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 192.168.1.255

# 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

on relance le service :

/etc/init.d/ntp restart

on verifie que les synchros se font bien :

ntpq -np

et on doit avoir quelque chose de similaire à

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 91.189.94.4     193.79.237.14    2 u   51   64    7   63.483    3.605   5.933
 91.121.92.90    81.25.192.148    3 u   52   64    7  896.272  427.251 427.431
 162.23.41.34    .HBGi.           1 u   50   64    7   65.701    6.408   7.775
 145.238.203.10  145.238.203.14   2 u   50   64    7   55.844    9.035   7.915
 134.157.254.19  10.3.128.189     2 u   48   64    7   39.268   -0.215   5.986
 193.51.24.1     .INIT.          16 u    -   64    0    0.000    0.000   0.000
 129.175.34.43   145.238.203.14   2 u   48   64    7   41.078    3.294   5.110
 195.13.23.5     195.13.23.6      2 u   48   64    7   51.399    2.123  10.906

la valeur "reach" doit augmenter avec le temps (en partant de 1) et tant qu'elle n'est pas à 7, les clients ne peuvent pas se synchroniser sur ce serveur.