End the NTP service for Linux servers

Ntp:network Time Protocol is a protocol used to synchronize the timing of a computer, which allows the computer to synchronize its server or clock source (such as a quartz clock, GPS, and so on) to provide a high-precision time correction (less than 1 milliseconds between the LAN and the standard difference, Dozens of MS on the WAN), and can be referred to as a cryptographic acknowledgment to prevent malicious protocol attacks.

1. Installation:

Yum Install Ntpyum Install Tzdata

The NTP protocol uses the udp,port:123

2. Configuration file:

/etc/ntp.conf #NTF服务器的主配置文件.

/usr/share/zoneinfo #由tzdata所提供的为各时区的时间格式式对应的文件.

/etc/sysconfig/clock #设置时区是否使用UTC时钟的配置文件. Our general choice of time zone is/usr/share/zoneinfo/asia/shanghai

/etc/localtime #本地终端的时间配置文件, if the clock file specifies that the time setting file used for the/usr/share/zoneinfo/asia/shanghai,linux operating system will Shanghai that file Copying a copy is/etc/localtime, so the time display of the system will be based on the Shanghai time setting file.

Driftfile: Record time Variance in the format: driftfile [Full path name], which is defined in/etc/ntp.conf.

3. Configuration

Configuring an upstream NTP server

vim/etc/ntp.conf# Add the following content restrict 133.100.11.8restrict 192.168.1.0 mask 255.255.255.0 nomodifyserver 133.100.11.8 prefer# allows the upstream server to 133.100.11.8 through, and specifies that the upstream server is 133.100.11.8 and is set to the first server.

Restrict administrative rights control

Ignore: Deny all types of connections

Nomodify: The client cannot use the NTPC and NTPQ to modify the server's time parameters, but the client can still access the network via this host.

Noquery: The client cannot use both NTPC and NTPQ to query the time server, which is equal to not providing NTP network.

Notrap: does not provide the ability to trap this remote event login (logging).

Notrust: Denies clients that are not authenticated.

4. Start

Start NTP after configuration is complete

Service NTPD Start

5. View status

NETSTAT-TUNLP | grep NTP

Ntpstat: Lists whether to connect to the upstream server

Ntpq-p: Lists the connection status of our NTP server to the upstream server,

Ntpq-p Remote refID St T when poll reach delay offset jitter======================================================== ======================*133.100.11.8 133.100.53.51 2 u 194.077 48.430 57.956+dns2.synet.edu. 202.118.1.46 2 U 177 60.418 9.773 53.180dns.sjtu.edu.cn. Init. u-1024 0 0.000 0.000 0.000+dns1.synet.edu. 223.255.185.2 2 U 210 128 176 104.460-22.500 25.028

REMOT:NTP the IP or domain name of the upstream host, * indicates that the upper ntp,+ currently in use indicates a successful connection and can be used as a candidate for the next delivery time update.

refID: Reference to the previous layer of NTP server address

ST: it is the stratum stratum

When: A few seconds ago there was time to synchronize the update operation.

Poll: The next update is after a few seconds.

Reach: The number of times the update has been requested for the upper NTP server.

Delay: The time that is delayed during network transmission, in units of 10-6 seconds

Offset: The result of the time compensation, in 10-3 seconds.

Jitter:linux the time difference between the system time and the BIOS hardware time.

6. Time correction

The time in Linux is divided into:

Software clock: Linux own system time, starting from January 1, 1970 to record the time parameters. Modified with date.

Hardware clock: The actual time recorded by the computer system in the BIOS, which is the time recorded by the hardware. Modified with Hwclock.

Hwclock-r: Read the time parameters of the BIOS

Hwclock-w: Writes the current system time to the BIOS.

Network School-time Method:

1. Manual Time: Ntpdate ntp_server

2. Automatic School Hours:

A. Scripting:

B. Scheduled tasks:

CRONTAB-E10 * * * * Root (/usr/sbin/ntpdate 192.168.1.107 &&/bin/hwclock-w) &>/dev/null

C. The client initiates the NTP service, which is automatically calibrated. In/etc/ntp.conf configuration,

Restrict 192.168.1.107server 192.168.1.107

Start the service

Service NTPD start; Chkconfig ntpd on

Note: The NTP service will run normally after the boot is complete, and I will wait for almost 5 minutes, otherwise Windows would provide the following error.

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The update was successful.

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Attached: Available Timing Center Address:

133.100.11.8 prefer
210.72.145.44
203.117.180.36
131.107.1.10