NTP 服务器在端口 123/313 上可用
nc -v -u -z -w 3 1.rhel.pool.ntp.org 123
Connection to 1.rhel.pool.ntp.org 123 port [udp/ntp] succeeded!
nc -v -u -z -w 3 2.rhel.pool.ntp.org 123
Connection to 2.rhel.pool.ntp.org 123 port [udp/ntp] succeeded!
nc -v -u -z -w 3 3.rhel.pool.ntp.org 123
Connection to 3.rhel.pool.ntp.org 123 port [udp/ntp] succeeded!
nc -v -u -z -w 3 1.rhel.pool.ntp.org 313
Connection to 1.rhel.pool.ntp.org 313 port [udp/magenta-logic] succeeded!
nc -v -u -z -w 3 0.rhel.pool.ntp.org 313
Connection to 0.rhel.pool.ntp.org 313 port [udp/magenta-logic] succeeded!
nc -v -u -z -w 3 2.rhel.pool.ntp.org 313
Connection to 2.rhel.pool.ntp.org 313 port [udp/magenta-logic] succeeded!
nc -v -u -z -w 3 3.rhel.pool.ntp.org 313
Connection to 3.rhel.pool.ntp.org 313 port [udp/magenta-logic] succeeded
ntpdate -d server 1.rhel.pool.ntp.org
26 Sep 07:31:23 ntpdate[17394]: ntpdate [email protected] Wed Dec 19 20:22:35 UTC 2018 (1)
Looking for host server and service ntp
Error resolving server: Name or service not known (-2)
26 Sep 07:31:23 ntpdate[17394]: Can't find host server: Name or service not known (-2)
Looking for host 1.rhel.pool.ntp.org and service ntp
host found : time.vedur.is
transmit(130.208.87.151)
transmit(193.4.58.77)
transmit(130.208.87.151)
transmit(193.4.58.77)
transmit(130.208.87.151)
transmit(193.4.58.77)
transmit(130.208.87.151)
transmit(193.4.58.77)
transmit(130.208.87.151)
transmit(193.4.58.77)
130.208.87.151: Server dropped: no data
193.4.58.77: Server dropped: no data
server 130.208.87.151, port 123
stratum 0, precision 0, leap 00, trust 000
refid [130.208.87.151], delay 0.00000, dispersion 64.00000
transmitted 4, in filter 4
reference time: 00000000.00000000 Sun, Dec 31 1899 22:32:12.000
originate timestamp: 00000000.00000000 Sun, Dec 31 1899 22:32:12.000
transmit timestamp: e6dbd3ce.54b42604 Mon, Sep 26 2022 7:31:26.330
filter delay: 0.00000 0.00000 0.00000 0.00000
0.00000 0.00000 0.00000 0.00000
filter offset: 0.000000 0.000000 0.000000 0.000000
0.000000 0.000000 0.000000 0.000000
delay 0.00000, dispersion 64.00000
offset 0.000000
server 193.4.58.77, port 123
stratum 0, precision 0, leap 00, trust 000
refid [193.4.58.77], delay 0.00000, dispersion 64.00000
transmitted 4, in filter 4
reference time: 00000000.00000000 Sun, Dec 31 1899 22:32:12.000
originate timestamp: 00000000.00000000 Sun, Dec 31 1899 22:32:12.000
transmit timestamp: e6dbd3ce.87e7ac7b Mon, Sep 26 2022 7:31:26.530
filter delay: 0.00000 0.00000 0.00000 0.00000
0.00000 0.00000 0.00000 0.00000
filter offset: 0.000000 0.000000 0.000000 0.000000
0.000000 0.000000 0.000000 0.000000
delay 0.00000, dispersion 64.00000
offset 0.000000
26 Sep 07:31:27 ntpdate[17394]: no server suitable for synchronization found
chrony.conf 文件：
# Please consider joining the pool (http://www.pool.ntp.org/join.html).
server 0.rhel.pool.ntp.org iburst
server 1.rhel.pool.ntp.org iburst
server 2.rhel.pool.ntp.org iburst
server 3.rhel.pool.ntp.org iburst
# Ignore stratum in source selection.
stratumweight 0
# Record the rate at which the system clock gains/losses time.
driftfile /var/lib/chrony/drift
# In first three updates step the system clock instead of slew
# if the adjustment is larger than 10 seconds.
makestep 1.0 3
# Enable kernel synchronization of the real-time clock (RTC).
rtcsync
# Allow NTP client access from local network.
# allow 192.168.10/24
# Serve time even if not synchronized to any NTP server.
#local stratum 10
# Specify file containing keys for NTP and command authentication.
#keyfile /etc/chrony.keys
# Specify key number for command authentication.
commandkey 1
# Generate new command key on start if missing.
generatecommandkey
minsources 3
# Disable logging of client accesses.
noclientlog
# Send message to syslog when clock adjustment is larger than 0.5 seconds.
logchange 0.5
# Specify directory for log files.
logdir /var/log/chrony
# Select which information is logged.
log measurements statistics tracking
iptables 已关闭
答案1
123 端口上的 Internet NTP 服务器传入流量被阻止。网络部门开放本地服务器的传入流量后，便能够同步时间。