Difference between revisions of "Network Time Protocol"
From Christoph's Personal Wiki
(New page: '''Network Time Protocol''' ('''NTP''') is a networking protocol for clock synchronization between computer systems over packet-switched, variable-latency data networks. ==Install and con...) |
(→Install and configure ntpd on CentOS) |
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$ ntpdc -l | $ ntpdc -l | ||
$ ntpdc -p | $ ntpdc -p | ||
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+ | * Use <code>[[tcpdump]]</code> to watch the NTP traffic: | ||
+ | $ tcpdump dst port 123 | ||
==External links== | ==External links== |
Revision as of 09:16, 19 May 2014
Network Time Protocol (NTP) is a networking protocol for clock synchronization between computer systems over packet-switched, variable-latency data networks.
Install and configure ntpd
on CentOS
- Install the necessary packages:
$ yum install ntp ntpdate ntp-doc
- Turn on the
ntpd
service persistently:
$ chkconfig ntpd on
- Synchronize the system clock with
0.pool.ntp.org
server:
$ ntpdate pool.ntp.org
- Start the NTP server. The following will continuously adjusts system time from upstream NTP server (i.e., o need to run
ntpdate
):
$ /etc/init.d/ntpd start $ #~OR~ $ service ntpd start
- Locate your geographically closets server pool from http://www.pool.ntp.org/en/
$ for i in africa asia europe north-america south-america; do \ curl -s http://www.pool.ntp.org/zone/$i|sed -n -e '/<pre>/,/<\/pre>/p'|sed -e 's/<[^>]*>//g'; done server 0.africa.pool.ntp.org server 1.africa.pool.ntp.org server 2.africa.pool.ntp.org server 3.africa.pool.ntp.org server 0.asia.pool.ntp.org server 1.asia.pool.ntp.org server 2.asia.pool.ntp.org server 3.asia.pool.ntp.org server 0.europe.pool.ntp.org server 1.europe.pool.ntp.org server 2.europe.pool.ntp.org server 3.europe.pool.ntp.org server 0.north-america.pool.ntp.org server 1.north-america.pool.ntp.org server 2.north-america.pool.ntp.org server 3.north-america.pool.ntp.org server 0.south-america.pool.ntp.org server 1.south-america.pool.ntp.org server 2.south-america.pool.ntp.org server 3.south-america.pool.ntp.org
- Since I am in North America, I will add the lines above for North America to the following two files:
$ cat >> /etc/ntp.conf <<EOF server 0.north-america.pool.ntp.org server 1.north-america.pool.ntp.org server 2.north-america.pool.ntp.org server 3.north-america.pool.ntp.org EOF $ cat >> /etc/ntp/step-tickers <<EOF 0.north-america.pool.ntp.org 1.north-america.pool.ntp.org 2.north-america.pool.ntp.org 3.north-america.pool.ntp.org EOF
- Finally, restart the NTP daemon:
$ service ntpd restart
- You can also list out your server pools and get details with the following:
$ ntpdc -l $ ntpdc -p
- Use
tcpdump
to watch the NTP traffic:
$ tcpdump dst port 123