我正在嘗試為 VPC 內的少數 EC2 執行個體開啟 NTP，從 ntpdate 開始，因為我的伺服器距離很遠，我不希望它發生故障。
我遇到了“沒有適合同步的伺服器”錯誤：
bash-4.1$ sudo ntpdate -u 0.amazon.pool.ntp.org
2 Oct 16:21:05 ntpdate[20767]: no server suitable for synchronization found
已經有一些關於此錯誤的帖子，並且它通常與防火牆規則相關。
眼下：
- 該實例在所有連接埠上打開，包括進出（不僅僅是 UDP/123）。
- 網路 ACL 在所有連接埠（輸入和輸出）上開啟
- DNS 已開啟，並且 0.amazon.pool.ntp.org 正在解析為實際位址。
- NAT 似乎正在運行，能夠使用 wget 到達其他外部位址（也可以解析 0.amazon.pool.ntp.org）
顯然我不能讓伺服器永遠開放，這只是試圖診斷問題。我不知道還能打開什麼。
這是診斷追蹤：
2 Oct 16:25:06 ntpdate[20815]: ntpdate [email protected] Mon Mar 9 14:24:09 UTC 2015 (1)
Looking for host 0.amazon.pool.ntp.org and service ntp
host found : services.quadranet.com
transmit(198.55.111.50)
transmit(50.116.55.65)
transmit(108.61.194.85)
transmit(173.44.32.10)
transmit(198.55.111.50)
transmit(50.116.55.65)
transmit(108.61.194.85)
transmit(173.44.32.10)
transmit(198.55.111.50)
transmit(50.116.55.65)
transmit(108.61.194.85)
transmit(173.44.32.10)
transmit(198.55.111.50)
transmit(50.116.55.65)
transmit(108.61.194.85)
transmit(173.44.32.10)
transmit(198.55.111.50)
transmit(50.116.55.65)
transmit(108.61.194.85)
transmit(173.44.32.10)
198.55.111.50: Server dropped: no data
50.116.55.65: Server dropped: no data
108.61.194.85: Server dropped: no data
173.44.32.10: Server dropped: no data
server 198.55.111.50, port 123
stratum 0, precision 0, leap 00, trust 000
refid [198.55.111.50], delay 0.00000, dispersion 64.00000
transmitted 4, in filter 4
reference time: 00000000.00000000 Sun, Dec 31 1899 19:00:00.000
originate timestamp: 00000000.00000000 Sun, Dec 31 1899 19:00:00.000
transmit timestamp: d9b966a5.c841bbbb Fri, Oct 2 2015 16:25:09.782
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 50.116.55.65, port 123
stratum 0, precision 0, leap 00, trust 000
refid [50.116.55.65], delay 0.00000, dispersion 64.00000
transmitted 4, in filter 4
reference time: 00000000.00000000 Sun, Dec 31 1899 19:00:00.000
originate timestamp: 00000000.00000000 Sun, Dec 31 1899 19:00:00.000
transmit timestamp: d9b966a5.fb750a47 Fri, Oct 2 2015 16:25:09.982
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 108.61.194.85, port 123
stratum 0, precision 0, leap 00, trust 000
refid [108.61.194.85], delay 0.00000, dispersion 64.00000
transmitted 4, in filter 4
reference time: 00000000.00000000 Sun, Dec 31 1899 19:00:00.000
originate timestamp: 00000000.00000000 Sun, Dec 31 1899 19:00:00.000
transmit timestamp: d9b966a6.2ea83387 Fri, Oct 2 2015 16:25:10.182
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 173.44.32.10, port 123
stratum 0, precision 0, leap 00, trust 000
refid [173.44.32.10], delay 0.00000, dispersion 64.00000
transmitted 4, in filter 4
reference time: 00000000.00000000 Sun, Dec 31 1899 19:00:00.000
originate timestamp: 00000000.00000000 Sun, Dec 31 1899 19:00:00.000
transmit timestamp: d9b966a6.61db63f1 Fri, Oct 2 2015 16:25:10.382
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
2 Oct 16:25:11 ntpdate[20815]: no server suitable for synchronization found
請提出建議？