Linux configuration NTP server method _linux

I. Installing the NTP software

1. Check if the NTP-related package is installed.
Rpm-qa | grep NTP

2. Install NTP software.
Yum-y Install NTP

Two. Parameter explanation

Ignore: Turn off all NTP Online Services

Nomodify: The client cannot change the time parameter of the server, but the client can use the server to do the network school.

Notrust: Client sources will be treated as untrusted subnets unless authenticated

Noquery: Do not provide client time query: User side can not use NTPQ,NTPC and other commands to query NTP server

Notrap: Do not provide trap remote login: Deny mode 6 control message Trap Service for matching hosts. The Trap service is the subsystem of the NTPDQ Control Message protocol, used for remote event logging programs.

Nopeer: Used to prevent the host from attempting to peer to the server and allow the rogue server to control the clock

Kod: Send Kod package when access violation.

Three. Modify the configuration file

1. View the unmodified configuration file

# grep ^[^#]/etc/ntp.conf  
driftfile/var/lib/ntp/drift
restrict default nomodify notrap
nopeer Restrict 127.0.0.1
Restrict:: 1
Server 0.centos.pool.ntp.org iburst
server 1.centos.pool.ntp.org iburst
server 2.centos.pool.ntp.org iburst
server 3.centos.pool.ntp.org iburst
INCLUDEFILE/ETC/NTP/CRYPTO/PW
Keys/etc/ntp/keys
Disable monitor

1. Set a client that allows any IP to synchronize time (modified profile)

# grep ^[^#]/etc/ntp.conf  
driftfile/var/lib/ntp/drift
restrict default nomodify notrap
restrict 127.0.0.1
Restrict:: 1
Server 0.centos.pool.ntp.org iburst
server 1.centos.pool.ntp.org iburst
Server 2.centos.pool.ntp.org iburst
server 3.centos.pool.ntp.org iburst
INCLUDEFILE/ETC/NTP/CRYPTO/PW
Keys/etc/ntp/keys
Disable monitor

2. Allow time synchronization only for clients with 192.168.1.0 network segment (modified configuration file)

# grep ^[^#]/etc/ntp.conf 
driftfile/var/lib/ntp/drift
restrict default nomodify notrap
nopeer Restrict 127.0.0.1
Restrict:: 1
Restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap
server 0. centos.pool.ntp.org iburst
Server 1.centos.pool.ntp.org iburst
server 2.centos.ntp.org iburst
server 3. centos.pool.ntp.org iburst
includefile/etc/ntp/crypto/pw
keys/etc/ntp/keys
Disable monitor

Four. Start NTP service and firewall

Systemctl Start NTPD
Systemctl Enable NTPD
Iptables-a input-p udp-i eno16777736-s 192.168.1.0/24--dport 123-j ACCEPT
Setsebool-p Ntp_disable_trans 1#selinux Settings
vi/etc/sysconfig/ntpd# allows the BIOS to synchronize with the system time, adding the following line.
Sync_hwclock=yes

Five. Detect NTP

1. Detect if NTP service is running

# NETSTAT-TLUNP | grep NTP
UDP    0   0 192.168.1.101:123    0.0.0.0:*              2563/ntpd     
UDP    0   0 127.0.0.1:123      0.0.0.0:*              2563/ntpd     
UDP    0   0 0.0.0.0:123       0.0.0.0:*              2563/ntpd     
udp6    0   0 fe80::20c:29ff:fe7b:123:::*                2563/ntpd     
udp6    0   0:: 1:123         :::*                2563/ntpd     
udp6    0   0:: 123         :::*                2563/ntpd 

2. See if the NTP server is connected to the upper level NTP

# Ntpstat
Synchronised to NTP Server (120.25.108.11) in stratum 3 time
  correct to within the MS
  polling Serv ER every

3. View the status of NTP server and upper NTP

# ntpq-p
   remote      refid   St T when poll reach  delay  offset jitter
============================= =================================================
 news.neu.edu.cn. INIT.     U  -  0  0.000  0.000  0.000
x202.118.1.130  202.118.1.47   2 U  7  377 153.659  9.605 19.941
*time4.aliyun.co 10.137.38.86   2 U 377  39.666- 47.661 15.944
Remote  -native and upper NTP IP or host name, "+" is preferred, "*" is the secondary priority
refID  -Reference up to the NTP host address
St    - Stratum class
When   -how many seconds ago has synchronized time
poll   -the next update in how many seconds after reach  -the number of times that the upper NTP server has been asked to update
delay  -Network delay
offset  -time compensation
jitter  -system time and BIOS lag

Six. Configure time synchronization Client

1. Execute ntpdate command:

Ntpdate 192.168.1.101 #192.168.1.101 for NTP server IP address

2. Write to Bios

Hclock-w

3.crond Service

Vi/etc/crontab
8 * * * root/usr/sbin/ntpdate 192.168.1.101; /sbin/hwclock-w

4. Restart Crond Service

Service Crond Restart

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