RDATE,NTPDATE,NTP Automatic synchronization Date-time method under Linux

Automatic synchronization via network NTP

If you only need to sync once, execute the following command

Rdate-s time.nist.gov

Where time.nist.gov is a time server, of course you can also use another time server.

If multiple servers require a full synchronization of time, it is best to configure these servers with a unified, automatic synchronization task, so that their time is biased for a variety of reasons. Methods are as follows

Use crontab to let Linux automatically sync time

Vi/etc/crontab

Add a sentence:

0 1 * * Root rdate-s time.nist.gov

Time.nist.gov is a time server.

Rdate Sync Configuration

CentOS minimized installation is not installed by default, first confirm already installed, otherwise install first.

Where Rdate itself is used to obtain time on a remote time server, with the-s parameter, you can apply the acquired time to the local system.

NAME
Rdate-get the time via the network

Synopsis
Rdate [-P] [s] [-u] [-l] [-t sec] [host ...]

DESCRIPTION
Rdate connects to an RFC www.111cn.net 868 time server over a TCP/IP network, printing the returned time
and/or setting the system clock.

OPTIONS
-P Print The time returned by the remote machine.

-S Set the system time to the returned time.

-U use UDP instead of TCP as the transport.

-l use Syslog to output errors (cron.warning) and output (Cron.info).

-T Set timeout in seconds for every attempt to retreive date.

Rdate-s time.nist.gov

Ntpdate itself is the tool used to synchronize time.

Example: Ntpdate ntp.sjtu.edu.cn

NAME
Ntpdate-set the date and time via NTP

Disclaimer:the functionality of the This are now available in the NTPD program. The-q com-
Mand line option in the Ntpd-network time Protocol (NTP) daemon page. After a suitable period of
Mourning, the Ntpdate program are to being retired from this distribution

Synopsis
ntpdate [ -46BBDQSUV] [-a key] [e-Authdelay] [-K keyfile] [-o version] [-p samples] [t
Timeout] [-u user_name] server [...]

DESCRIPTION

[Refer to the Linux Man manual]

Linux Cluster time synchronization

Plans to sync 11 Linux cluster times, operating system for Ubuntu 11.04 x86 64-bit
Select one of the 133.133.10.2 as the time server (NTP server), while the other nodes are synchronized with the node.

1, install NTP server on 133.133.10.2 (monitor).
root@monitor:~# Apt-get Install NTP

2. Modify/etc/ntp.conf


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

Driftfile/var/lib/ntp/ntp.drift


# Enable This if you are 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

# Specify one or more NTP servers.

# Use servers from the NTP Pool Project. Approved by Ubuntu Technical Board
# on 2011-02-08 (LP: #104525). Http://www.pool.ntp.org/join.html for
# more information.
#server 0.ubuntu.pool.ntp.org
#server 1.ubuntu.pool.ntp.org
#server 2.ubuntu.pool.ntp.org
#server 3.ubuntu.pool.ntp.org

# use Ubuntu ' s NTP server as a fallback.
#server ntp.ubuntu.com
Server 127.127.1.0 minpoll 4 maxpoll 5
Fudge 127.127.1.0 Stratum 2

# Access control configuration; See/usr/share/doc/ntp-doc/html/accopt.html for
# details. The Web page # might also be helpful.
#
# "Restrict" applies to both servers and clients, so a configuration
# that might is intended to the requests from certain clients could
# 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-4 Default Kod nomodify noper
restrict-6 Default Kod nomodify noper

# Local Users may interrogate the NTP server more closely.
Restrict 127.0.0.1
Restrict:: 1

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


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

# If you are want to listen to broadcasts on your local subnet, de-comment the
# Next lines. Please does this is only if your everybody on the network!
#disable Auth
#broadcastclient

3. Run ntpdate command

First restart the NTP service
ROOT@MONITOR:/ETC#/ETC/INIT.D/NTP restart

Run again
root@monitor:/etc# ntpdate-q 127.0.0.1
Get
Server 127.0.0.1, stratum 3, offset-0.000003, delay 0.02565
Sep 17:12:00 ntpdate[11502]: Adjust time server 127.0.0.1 offset-0.000003 sec

4, the other nodes 133.133.10.* time and 133.133.10.2 synchronization

Run commands on every other node

root@slave1:~# ntpdate 133.133.10.2

At this time to find the synchronization between the nodes, but ntpdate only on the run, we want to set to 1-hour sync, then proceed to step 5th

5, the other nodes 133.133.10.* time and 133.133.10.2 synchronization

Use crontab to automatically update the time after installation:
#crontab-E
Add the following line:
* */1 * * * */usr/sbin/ntpdate 133.133.10.2

This line means that each hour is synchronized with the 133.133.10.2 time.

6, through the date command found all nodes time is the same