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Table of Contents
NTP
It is best to use pool.ntp.org as an NTP server. This will find the closest available servers for you.
Also
- pool.ntp.org
- 0.pool.ntp.org
- 1.pool.ntp.org
- 2.pool.ntp.org
- 3.pool.ntp.org
More specific are:
- ntp0.ja.net (Stratum 1)
- ntp1.npl.co.uk (Stratum 2)
- time.cloudflare.com (Stratum 3)
- uk.pool.ntp.org
- 0.uk.pool.ntp.org
- 1.uk.pool.ntp.org
- 2.uk.pool.ntp.org
- 3.uk.pool.ntp.org
- europe.pool.ntp.org
- 0.europe.pool.ntp.org
- 1.europe.pool.ntp.org
- 2.europe.pool.ntp.org
- 3.europe.pool.ntp.org
The 0, 1, 2 and 3.pool.ntp.org names point to a random set of servers that will change every hour.
Testing Windows NTP
You can test NTP manually using Windows using the following command (where 192.168.1.1 is the IP of the NTP server).
w32tm /stripchart /dataonly /computer:192.168.1.1
Resynchronize the clock
w32tm /resync
Show current timezone settings
w32tm /tz
List external NTP servers (peers)
w32tm /query /peers
REMEMBER It is important to note that W32Time will only actively synchronize with one time source at a time, even though you are able to list more than one time source. (source)
Most NTP implementations would poll all the servers to choose the best sample, but as of Server 2008, Windows doesn't. That may have changed since then, but it isn't very documented.
w32tm /config /manualpeerlist:0.nl.pool.ntp.org,1.nl.pool.ntp.org,2.nl.pool.ntp.org,3.nl.pool.ntp.org,0x1 /syncfromflags:MANUAL /reliable:yes /update ; net stop w32time ; net start w32time ; w32tm /query /peers /verbose
w32tm /config /manualpeerlist:time.cloudflare.com,0x1 /syncfromflags:MANUAL /reliable:yes /update ; net stop w32time ; net start w32time ; w32tm /query /peers /verbose
Set Linux Time
sudo date -s "22 JUN 2020 13:11:30"
Check Status
Check status of NTP on Ubuntu 16.04+
timedatectl status
If NTP is not on, try the following command
sudo timedatectl set-ntp on
NTP Servers
List of Stratum 1 servers
National Physics Laboratory hosts two public “Stratum 2” servers. This means their servers sync directly to atomic clocks.
DO NOT configure your system to use Google Public NTP together with non-leap-smearing NTP servers. e.g. do not combine Google NTP with Cloudflare NTP as they do not implement leap smearing. Smearing is used by Google, AWS, and Facebook NTP servers but not Cloudflare.
| Operator | Server FQDN | Server IP | Stratum | RefID | Source Type or FQDN | Delay | Location | Supports iBurst |
|---|---|---|---|---|---|---|---|---|
| Cloudflare | time.cloudflare.com | 162.159.200.1 | 3 | 10.21.8.19 | Internal Cloudflare? | 13.080 | UK | |
| Cloudflare | time.cloudflare.com | 162.159.200.123 | 3 | 10.21.8.19 | Internal Cloudflare? | 13.896 | UK | |
| Microsoft | time.windows.com | 51.145.123.29 | 3 | 25.66.230.5 | Internal Microsoft? | 13.896 | UK | |
| Zen Internet | ntp0.zen.co.uk | 212.23.8.6 | 2 | 195.66.241.3 | ntp1.linx.net | 11.642 | ||
| Zen Internet | ntp1.zen.co.uk | 212.23.10.129 | 2 | 85.199.214.99 | server1.quickdrivingtestcancellations.net | 16.948 | UK | |
| National Physics Laboratory | ntp1.npl.co.uk | 139.143.5.30 | 2 | 139.143.45.169 | ? | 16.457 | UK | |
| National Physics Laboratory | ntp2.npl.co.uk | 139.143.5.31 | 2 | 139.143.45.169 | ? | 17.329 | UK | |
| Manchester University | ntp2a.mcc.ac.uk | 130.88.202.49 | 2 | 193.62.22.66 | ntp0.ja.net | 22.581 | UK | |
| Manchester University | ntp2b.mcc.ac.uk | 130.88.203.13 | 2 | 130.88.203.13 | ntp0.ja.net | 22.282 | UK | |
| Manchester University | ntp2c.mcc.ac.uk | 130.88.200.6 | 2 | 193.62.22.66 | ntp0.ja.net | 22.135 | UK | |
| Manchester University | ntp2d.mcc.ac.uk | 130.88.212.143 | 2 | 193.62.22.74 | ntp1.ja.net | 22.771 | UK | |
| JANET, Harwell | ntp0.ja.net | 193.62.22.66 | 1 | .MSF. | MSF Radio Clock Receiver | 15.981 | UK | |
| JANET, Harwell | ntp1.ja.net | 193.62.22.74 | 1 | .MRS. | N/A | 26.042 | UK | |
| JANET, Harwell | ntp2.ja.net | 193.62.22.98 | 2 | 193.62.22.74 | ntp1.ja.net | 22.849 | UK | |
| JANET, Harwell | ntp3.ja.net | 193.62.22.90 | 1 | .PPS. | N/A | 26.305 | UK | |
| JANET, Harwell | ntp4.ja.net | 193.62.22.82 | 1 | .DCFa. | DCF77 | 17.528 | UK | |
| time.google.com | time1-time4 | 1 | Yes | |||||
| time1.google.com | 216.239.35.0 | 1 | .GOOG. | N/A | 20.393 | Yes | ||
| time2.google.com | 216.239.35.4 | 1 | .GOOG. | N/A | 20.399 | Yes | ||
| time3.google.com | 216.239.35.8 | 1 | .GOOG. | N/A | 20.514 | Yes | ||
| time4.google.com | 216.239.35.12 | 1 | .GOOG. | N/A | 22.899 | Yes | ||
| time.facebook.com | time1-time5 | 1 | Yes | |||||
| time1.facebook.com | 129.134.28.123 | 1 | .FB… | N/A | 25.595 | Yes | ||
| time2.facebook.com | 129.134.29.123 | 1 | .FB… | N/A | 16.803 | Yes | ||
| time3.facebook.com | 129.134.25.123 | 1 | .FB… | N/A | 12.037 | Yes | ||
| time4.facebook.com | 129.134.26.123 | 1 | .FB… | N/A | 18.341 | Yes | ||
| time5.facebook.com | 129.134.27.123 | 1 | .FB… | N/A | 16.546 | Yes | ||
| Apple | time.apple.com | 17.253.108.253 (and others) | 1 | .SHM. | 17.343 | Yes | ||
| Apple | time.euro.apple.com | 17.253.34.125 (and others) | 1 | .SHM. | 9.889 | Yes | ||
| Leo Bodnar Electronics | ntp1.leontp.com | 51.155.16.62 | 1 | .GPS. | N/A | 36.932 | UK | |
| Leo Bodnar Electronics | ntp5.leontp.com | 85.199.214.98 | 1 | .GPS. | N/A | 16.523 | UK | |
| Leo Bodnar Electronics | ntp6.leontp.com | 85.199.214.99 | 1 | .GPS. | N/A | 15.949 | UK | |
| Leo Bodnar Electronics | ntp7.leontp.com | 85.199.214.100 | 1 | .GPS. | N/A | 16.002 | UK | |
| Leo Bodnar Electronics | ntp8.leontp.com | 85.199.214.101 | 1 | .GPS. | N/A | 16.595 | UK | |
| Leo Bodnar Electronics | ntp9.leontp.com | 85.199.214.102 | 1 | .GPS. | N/A | 15.965 | UK | |
| Xentex IT Solutions | ntp.xtx.cloud | 81.133.66.177 | 1 | .PPS. | N/A | 24.301 | UK |
More information on Google's NTP offering can be found here. Google 'smear' a leap second over the course of a the hour either side of the leap second. Do not mix NTP servers that 'smear' and NTP servers that do not 'smear'.
Google uses its own NTP servers (see above) for its public DNS servers (see below). If you cannot configure multiple servers, time.google.com will automatically select an appropriate Google server nearby.