1. Segue o arquivo padrão fornecido pelo pacote de instalação:
# 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 0.debian.pool.ntp.org iburst
server 1.debian.pool.ntp.org iburst
server 2.debian.pool.ntp.org iburst
server 3.debian.pool.ntp.org 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
# 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
2. Modifique as linhas
server, substituindo pelo servidor NTP local; sendo uma linha para cada servidor:
server 0.debian.pool.ntp.org iburst
server 1.debian.pool.ntp.org iburst
server 2.debian.pool.ntp.org iburst
server 3.debian.pool.ntp.org iburst
Obs.: a flag
iburst, faz com que uma saraivada de mensagens sejam trocadas para preparar os dados e ajustar o relógio por cerca de 10 s.
Modificando para o NTP da NTP.br:
a.st1.ntp.br
b.st1.ntp.br
c.st1.ntp.br
d.st1.ntp.br
a.ntp.br
b.ntp.br
c.ntp.br
gps.ntp.br
Nota do
NTP.br: se você usa uma versão recente (4.2.6 ou superior) do NTPd, ou o OpenNTPD, pode usar também o seguinte pool DNS, para configurar todos os servidores de uma só vez:
pool.ntp.br
3. Reinicie o serviço NTP:
# /etc/init.d/ntpd restart
Ou:
# /etc/init.d/ntp restart
4. Agora, visualize como ficou o arquivo de configuração do serviço NTP:
# cat /etc/ntp.conf |grep -E -v "^$|^#" |nl
1 driftfile /var/lib/ntp/ntp.drift
2 statistics loopstats peerstats clockstats
3 filegen loopstats file loopstats type day enable
4 filegen peerstats file peerstats type day enable
5 filegen clockstats file clockstats type day enable
6 server a.st1.ntp.br iburst
7 server b.st1.ntp.br iburst
8 server c.st1.ntp.br iburst
9 server d.st1.ntp.br iburst
10 restrict -4 default kod notrap nomodify nopeer noquery
11 restrict -6 default kod notrap nomodify nopeer noquery
12 restrict 127.0.0.1
13 restrict ::1
5. Vale destacar essas opções interessantes no
ntp.conf que criam estatísticas do funcionamento do servidor NTP:
statsdir /var/log/ntpstats/ #(Esta linha não é obrigatória... mas não custa adicionar)
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