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The negativity about using the NTP pool seems unwarranted. The NTP pool monitors all servers in it and will kick out those who are supplying incorrect times or

by bradfa 5y ago

The negativity about using the NTP pool seems unwarranted. The NTP pool monitors all servers in it and will kick out those who are supplying incorrect times or who are unavailable. You're also much more likely to be able to easily find a pretty good and pretty local set of NTP servers if you use the NTP pool, versus needing to look up other addresses for NTP servers. You don't need to use your country code in the FQDN for using the NTP pool, the DNS resolution should do a pretty good job of figuring it out for you and giving you rather local servers in response. https://www.ntppool.org/en/use.html https://www.ntppool.org/en/use.html

shaicoleman 5y ago
I personally stopped using pool.ntp.org after hitting a production issue where one of the timeservers was off by an hour. Leap second issues are another reason to avoid pool.ntp.org, and I use now leap-smearing time services. I recommend using the Google Public NTP service (time.google.com) [1]. Under AWS I use the AWS Time Sync Service (169.254.169.123) [2] I guess this would be mitigated by querying multiple servers with a smarter NTP client that is able to query multiple servers and filter out invalid time data (e.g. chrony), but I'm not keen on finding out the hard way. 1. https://developers.google.com/time https://developers.google.com/time 2. https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/set-time.html https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/set-time...
- bradfa 5y ago
  The recommended way to use NTP is to run a daemon which will continue to run in the background ensuring your clock is accurate and to have it reference multiple time sources (or a known stratum 1 source, like an atomic clock, WWV station, GPS, etc). If you're just syncing your clock once at boot, Google's time servers are probably fine to use, any time server is probably fine to use. Your hardware clock is going to drift over time but lots of times that's perfectly OK. A pool server that's off by an hour would get kicked out of the pool within probably 20-40 minutes and not allowed back in until it was reporting the correct time for a reasonable duration. The current pool monitoring seems to go at a cadence of around 20 minutes to cycle through all the servers validating them. You can have a look at the log of the monitoring of one of my NTP pool servers: https://www.ntppool.org/scores/165.227.219.198/log?limit=200 https://www.ntppool.org/scores/165.227.219.198/log?limit=200
  - bradfa 5y ago
    For some pretty graphs, you can have a look at what the pool monitoring does for my pool servers: https://www.ntppool.org/a/bradfa https://www.ntppool.org/a/bradfa
  - shaicoleman 5y ago
    > The recommended way to use NTP is to run a daemon which will continue to run in the background ensuring your clock is accurate You'd might not want to have a daemon running in the background or install extra software in certain circumstances. If you're using a lightweight solution such as systemd-timesyncd or ntpdate+cron it will only query one server, and you end up with the wrong time for ~30 minutes, which can cause major downtime or data corruption in certain circumstances. Even if you're able to use a better client like chrony, it still doesn't solve the issues with leap seconds without extra configuration, which can cause the time to jump or move backwards, which can cause major downtime, e.g. https://blog.cloudflare.com/how-and-why-the-leap-second-affected-cloudflare-dns/ https://blog.cloudflare.com/how-and-why-the-leap-second-affe... https://www.techspot.com/news/49229-leap-second-bug-amazon-ec2-outage-brought-down-major-websites.html https://www.techspot.com/news/49229-leap-second-bug-amazon-e...
    - bradfa 5y ago
      Yes, adding ntpd or chrony is another package but they really aren’t that big or burdensome on modern embedded systems. If you can fit systemd you can probably fit a real time daemon, too. I could understand if you’re running in a system with single digit MB of ram or flash, maybe you can’t fit them, but those sizes systems today are quite rare.
- deleted 5y ago
  [deleted]

by bradfa 5y ago

shaicoleman 5y ago

I personally stopped using pool.ntp.org after hitting a production issue where one of the timeservers was off by an hour. Leap second issues are another reason to avoid pool.ntp.org, and I use now leap-smearing time services. I recommend using the Google Public NTP service (time.google.com) [1]. Under AWS I use the AWS Time Sync Service (169.254.169.123) [2] I guess this would be mitigated by querying multiple servers with a smarter NTP client that is able to query multiple servers and filter out invalid time data (e.g. chrony), but I'm not keen on finding out the hard way. 1. https://developers.google.com/time https://developers.google.com/time 2. https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/set-time.html https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/set-time...

bradfa 5y ago
The recommended way to use NTP is to run a daemon which will continue to run in the background ensuring your clock is accurate and to have it reference multiple time sources (or a known stratum 1 source, like an atomic clock, WWV station, GPS, etc). If you're just syncing your clock once at boot, Google's time servers are probably fine to use, any time server is probably fine to use. Your hardware clock is going to drift over time but lots of times that's perfectly OK. A pool server that's off by an hour would get kicked out of the pool within probably 20-40 minutes and not allowed back in until it was reporting the correct time for a reasonable duration. The current pool monitoring seems to go at a cadence of around 20 minutes to cycle through all the servers validating them. You can have a look at the log of the monitoring of one of my NTP pool servers: https://www.ntppool.org/scores/165.227.219.198/log?limit=200 https://www.ntppool.org/scores/165.227.219.198/log?limit=200
- bradfa 5y ago
  For some pretty graphs, you can have a look at what the pool monitoring does for my pool servers: https://www.ntppool.org/a/bradfa https://www.ntppool.org/a/bradfa
- shaicoleman 5y ago
  > The recommended way to use NTP is to run a daemon which will continue to run in the background ensuring your clock is accurate You'd might not want to have a daemon running in the background or install extra software in certain circumstances. If you're using a lightweight solution such as systemd-timesyncd or ntpdate+cron it will only query one server, and you end up with the wrong time for ~30 minutes, which can cause major downtime or data corruption in certain circumstances. Even if you're able to use a better client like chrony, it still doesn't solve the issues with leap seconds without extra configuration, which can cause the time to jump or move backwards, which can cause major downtime, e.g. https://blog.cloudflare.com/how-and-why-the-leap-second-affected-cloudflare-dns/ https://blog.cloudflare.com/how-and-why-the-leap-second-affe... https://www.techspot.com/news/49229-leap-second-bug-amazon-ec2-outage-brought-down-major-websites.html https://www.techspot.com/news/49229-leap-second-bug-amazon-e...
  - bradfa 5y ago
    Yes, adding ntpd or chrony is another package but they really aren’t that big or burdensome on modern embedded systems. If you can fit systemd you can probably fit a real time daemon, too. I could understand if you’re running in a system with single digit MB of ram or flash, maybe you can’t fit them, but those sizes systems today are quite rare.
deleted 5y ago
[deleted]