driftfile詳解：
我們每一個system clock的頻率都有小小的誤差,這個就是為什么機器運行一段時間后會不精確. NTP會自動來監測我們時鍾的誤差值並予以調整.
但問題是這是一個冗長的過程,所以它會把記錄下來的誤差先寫入driftfile.這樣即使你重新開機以后之前的計算結果也就不會丟失了。
[root@localhost etc]# cat ntp.conf
# For more information about this file, see the man pages
# ntp.conf(5), ntp_acc(5), ntp_auth(5), ntp_clock(5), ntp_misc(5), ntp_mon(5).
driftfile /var/lib/ntp/drift
driftfile詳解：
我們每一個system clock的頻率都有小小的誤差,這個就是為什么機器運行一段時間后會不精確. NTP會自動來監測我們時鍾的誤差值並予以調整.
但問題是這是一個冗長的過程,所以它會把記錄下來的誤差先寫入driftfile.這樣即使你重新開機以后之前的計算結果也就不會丟失了。
# Permit time synchronization with our time source, but do not
# permit the source to query or modify the service on this system.
restrict default nomodify notrap nopeer noquery
詳解：默認是拒絕所有來源的任何訪問
# Permit all access over the loopback interface. This could
# be tightened as well, but to do so would effect some of
# the administrative functions.
restrict 127.0.0.1
restrict ::1
詳解：開放本機的任何訪問
# Hosts on local network are less restricted.
#restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap
# Use public servers from the pool.ntp.org project.
# Please consider joining the pool (http://www.pool.ntp.org/join.html).
#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
server 172.16.10.129 iburst
詳解：指定ntp服務器地址
#broadcast 192.168.1.255 autokey # broadcast server
#broadcastclient # broadcast client
#broadcast 224.0.1.1 autokey # multicast server
#multicastclient 224.0.1.1 # multicast client
#manycastserver 239.255.254.254 # manycast server
#manycastclient 239.255.254.254 autokey # manycast client
# Enable public key cryptography.
#crypto
includefile /etc/ntp/crypto/pw
詳解：配置文件默認開啟
# Key file containing the keys and key identifiers used when operating
# with symmetric key cryptography.
keys /etc/ntp/keys
詳解：配置文件默認開啟
# Specify the key identifiers which are trusted.
#trustedkey 4 8 42
# Specify the key identifier to use with the ntpdc utility.
#requestkey 8
# Specify the key identifier to use with the ntpq utility.
#controlkey 8
# Enable writing of statistics records.
#statistics clockstats cryptostats loopstats peerstats
# Disable the monitoring facility to prevent amplification attacks using ntpdc
# monlist command when default restrict does not include the noquery flag. See
# CVE-2013-5211 for more details.
# Note: Monitoring will not be disabled with the limited restriction flag.
disable monitor