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42 lines
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42 lines
2.2 KiB
Markdown
# Notes on NTP Daemon Setup
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As mentioned [elsewhere in these docs](../nodes/setup-run-node.html), there are several NTP daemons available, including:
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* The reference NTP daemon from ntp.org; see [their support website](http://support.ntp.org/bin/view/Support/WebHome)
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* [OpenNTPD](http://www.openntpd.org/)
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* [chrony](https://chrony.tuxfamily.org/index.html)
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* Maybe [NTPsec](https://www.ntpsec.org/), once it's production-ready
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* Maybe [Ntimed](http://nwtime.org/projects/ntimed/), once it's production-ready
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* [More](https://en.wikipedia.org/wiki/Ntpd#Implementations)
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It's tricky to make an NTP daemon setup secure. Always install the latest version and read the documentation about how to configure and run it securely.
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## Ubuntu Packages
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The [Ubuntu 14.04 (Trusty Tahr) package `ntp`](https://launchpad.net/ubuntu/trusty/+source/ntp) is based on the reference implementation of an NTP daemon.
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The following commands will uninstall the `ntp` and `ntpdate` packages, install the latest `ntp` package (which _might not be based on the latest ntpd code_), and start the NTP daemon (a local NTP server). (`ntpdate` is not reinstalled because it's [deprecated](https://askubuntu.com/questions/297560/ntpd-vs-ntpdate-pros-and-cons) and you shouldn't use it.)
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```text
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sudo apt-get --purge remove ntp ntpdate
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sudo apt-get autoremove
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sudo apt-get update
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sudo apt-get install ntp
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# That should start the NTP daemon too, but just to be sure:
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sudo service ntp restart
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```
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You can check if NTP is running using `sudo ntpq -p`.
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You may want to use different NTP time servers. You can change them by editing the NTP config file `/etc/ntp.conf`.
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Note: A server running the NTP daemon can be used by others for DRDoS amplification attacks. The above installation procedure should install a default NTP configuration file `/etc/ntp.conf` with the lines:
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```text
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restrict -4 default kod notrap nomodify nopeer noquery
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restrict -6 default kod notrap nomodify nopeer noquery
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```
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Those lines should prevent the NTP daemon from being used in an attack. (The first line is for IPv4, the second for IPv6.)
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There are additional things you can do to make NTP more secure. See the [NTP Support Website](http://support.ntp.org/bin/view/Support/WebHome) for more details.
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