NTP - Revision history

Koalp: Add link to chrony article

2024-06-14T13:20:08Z

Add link to chrony article

← Older revision		Revision as of 13:20, 14 June 2024
Line 20:		Line 20:
	* for '''ntpd''', use <code>services.ntp.enable = true;</code>		* for '''ntpd''', use <code>services.ntp.enable = true;</code>
	* for '''openntpd''', use <code>services.openntpd.enable = true;</code>		* for '''openntpd''', use <code>services.openntpd.enable = true;</code>
	* for '''chrony''', use <code>services.chrony.enable = true;</code>		* for '''[[chrony]]''', use <code>services.chrony.enable = true;</code>

	== Set NTP from DHCP servers ==		== Set NTP from DHCP servers ==

Klinger: Category:Server Category:Cookbook

2024-04-19T17:51:36Z

Category:Server Category:Cookbook

← Older revision		Revision as of 17:51, 19 April 2024
Line 130:		Line 130:

	[[Category:Server]]		[[Category:Server]]
			[[Category:Cookbook]]

Klinger: Category:Server

2024-04-19T17:51:13Z

Category:Server

← Older revision		Revision as of 17:51, 19 April 2024
Line 128:		Line 128:
	</li>		</li>
	</ol>		</ol>

			[[Category:Server]]

imported>IgorM: Fixed highlighting in console examples

2023-09-26T09:12:50Z

Fixed highlighting in console examples

← Older revision		Revision as of 09:12, 26 September 2023
Line 25:		Line 25:

	Most of the time the default NTP servers will be reachable. However, sometimes the NTP servers can be blocked by the firewall (for instance most universities block NTP for security reasons). This will be visible in the <code>systemd-timesyncd.service</code>:		Most of the time the default NTP servers will be reachable. However, sometimes the NTP servers can be blocked by the firewall (for instance most universities block NTP for security reasons). This will be visible in the <code>systemd-timesyncd.service</code>:
	<syntaxHighlight lang=~~text~~>		<syntaxHighlight lang=console>
	$ sudo systemctl status systemd-timesyncd.service		$ sudo systemctl status systemd-timesyncd.service
	● systemd-timesyncd.service - Network Time Synchronization		● systemd-timesyncd.service - Network Time Synchronization
Line 34:		Line 34:

	You can also test a specific server as follows:		You can also test a specific server as follows:
	<syntaxHighlight lang=~~text~~>		<syntaxHighlight lang=console>
	$ nix-shell -p ntp		$ nix-shell -p ntp
	$ ntpdate -q 0.nixos.pool.ntp.org		$ ntpdate -q 0.nixos.pool.ntp.org
Line 41:		Line 41:

	However, a replacement NTP is usually provided in that case via the DHCP protocol. You can see it for instance if you use Network Manager:		However, a replacement NTP is usually provided in that case via the DHCP protocol. You can see it for instance if you use Network Manager:
	<syntaxHighlight lang=~~text~~>		<syntaxHighlight lang=console>
	$ nmcli connection show 'name-of-the-current-connection' \| grep ntp		$ nmcli connection show 'name-of-the-current-connection' \| grep ntp
	DHCP4.OPTION[8]: ntp_servers = 192.168.x.y		DHCP4.OPTION[8]: ntp_servers = 192.168.x.y
Line 51:		Line 51:

	You might also be able to get the actual hostname of the DHCP (if it exists) using:		You might also be able to get the actual hostname of the DHCP (if it exists) using:
	<syntaxHighlight lang=~~text~~>		<syntaxHighlight lang=console>
	$ sudo nmap -sP 192.168.x.y		$ sudo nmap -sP 192.168.x.y
	</syntaxHighlight>		</syntaxHighlight>
Line 118:		Line 118:

	To apply the change, switch to your new configuration and make sure to restart Network Manager:		To apply the change, switch to your new configuration and make sure to restart Network Manager:
	<syntaxHighlight lang=~~nix~~>		<syntaxHighlight lang=console>
	$ sudo systemctl restart NetworkManager.service		$ sudo systemctl restart NetworkManager.service
	# Check if the NTP server is used (may need to wait a few minutes)		</syntaxHighlight>
			Check if the NTP server is used (may need to wait a few minutes):
			<syntaxHighlight lang=console>
	$ sudo systemctl status systemd-timesyncd.service		$ sudo systemctl status systemd-timesyncd.service
	</syntaxHighlight>		</syntaxHighlight>

imported>IgorM: Fixed syntax highlighting errors by using lang=text where it was omitted

2023-09-26T08:41:31Z

Fixed syntax highlighting errors by using lang=text where it was omitted

← Older revision		Revision as of 08:41, 26 September 2023
Line 25:		Line 25:

	Most of the time the default NTP servers will be reachable. However, sometimes the NTP servers can be blocked by the firewall (for instance most universities block NTP for security reasons). This will be visible in the <code>systemd-timesyncd.service</code>:		Most of the time the default NTP servers will be reachable. However, sometimes the NTP servers can be blocked by the firewall (for instance most universities block NTP for security reasons). This will be visible in the <code>systemd-timesyncd.service</code>:
	<syntaxHighlight>		<syntaxHighlight lang=text>
	$ sudo systemctl status systemd-timesyncd.service		$ sudo systemctl status systemd-timesyncd.service
	● systemd-timesyncd.service - Network Time Synchronization		● systemd-timesyncd.service - Network Time Synchronization
Line 34:		Line 34:

	You can also test a specific server as follows:		You can also test a specific server as follows:
	<syntaxHighlight>		<syntaxHighlight lang=text>
	$ nix-shell -p ntp		$ nix-shell -p ntp
	$ ntpdate -q 0.nixos.pool.ntp.org		$ ntpdate -q 0.nixos.pool.ntp.org
Line 41:		Line 41:

	However, a replacement NTP is usually provided in that case via the DHCP protocol. You can see it for instance if you use Network Manager:		However, a replacement NTP is usually provided in that case via the DHCP protocol. You can see it for instance if you use Network Manager:
	<syntaxHighlight>		<syntaxHighlight lang=text>
	$ nmcli connection show 'name-of-the-current-connection' \| grep ntp		$ nmcli connection show 'name-of-the-current-connection' \| grep ntp
	DHCP4.OPTION[8]: ntp_servers = 192.168.x.y		DHCP4.OPTION[8]: ntp_servers = 192.168.x.y
Line 51:		Line 51:

	You might also be able to get the actual hostname of the DHCP (if it exists) using:		You might also be able to get the actual hostname of the DHCP (if it exists) using:
	<syntaxHighlight>		<syntaxHighlight lang=text>
	$ sudo nmap -sP 192.168.x.y		$ sudo nmap -sP 192.168.x.y
	</syntaxHighlight>		</syntaxHighlight>

imported>Tobias.bora at 14:28, 23 November 2022

2022-11-23T14:28:26Z

← Older revision		Revision as of 14:28, 23 November 2022
Line 57:		Line 57:
	Then, you can of course manually add the DHCP server as explained above… but it's not practical when you often go to new places, or if the NTP server changes over time. For laptop it may not be a big issue (your internal clock will be used in that case until you reach a new network without firewalls) but for some devices like raspberry pi that can't store the time when device is turned off, or for servers that will always be behind the firewall, it can be interesting to automatically configure the NTP server using DHCP.		Then, you can of course manually add the DHCP server as explained above… but it's not practical when you often go to new places, or if the NTP server changes over time. For laptop it may not be a big issue (your internal clock will be used in that case until you reach a new network without firewalls) but for some devices like raspberry pi that can't store the time when device is turned off, or for servers that will always be behind the firewall, it can be interesting to automatically configure the NTP server using DHCP.

	The procedure depends on how you configure internet. By default (if you have not installed network manager…) the [https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/tasks/network-interfaces-scripted.nix module <code>network-interfaces-scripted</code>] will be used… unfortunately as far as I know this script cannot deal with NTP.		The procedure depends on how you configure internet:
			<ol>
	If you use <code>systemd-networkd</code>, then it should automatically use the right NTP… However if you want the configuration to be automatic you want to use <code>networking.useNetworkd = true;</code> instead of <code>systemd.network.enable</code> (<code>useNetworkd</code> will automatically configure <code>systemd.network</code> to provide a good default experience as alone <code>systemd.network</code> does basically nothing). However, <code>networking.useNetworkd</code> is apparently experimental now (2022) according to its documentation, so use it at your own risks. As far as I understand you can also '''disable''' the default behavior using:		<li> '''By default''': (if you have not installed network manager…) the [https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/tasks/network-interfaces-scripted.nix module <code>network-interfaces-scripted</code>] will be used… unfortunately as far as I know this script cannot deal with NTP. </li>
			<li> '''networkd''': If you use <code>systemd-networkd</code>, then it should automatically use the right NTP… However if you want the configuration to be automatic you want to use <code>networking.useNetworkd = true;</code> instead of <code>systemd.network.enable</code> (<code>useNetworkd</code> will automatically configure <code>systemd.network</code> to provide a good default experience as alone <code>systemd.network</code> does basically nothing). However, <code>networking.useNetworkd</code> is apparently experimental now (2022) according to its documentation, so use it at your own risks. As far as I understand you can also '''disable''' the default behavior using:
	<syntaxHighlight lang=nix>		<syntaxHighlight lang=nix>
	systemd.network.config = {		systemd.network.config = {
Line 67:		Line 68:
	</syntaxHighlight>		</syntaxHighlight>
	but I have not tested it.		but I have not tested it.
			</li>
	If you use Network Manager, then Network Manager cannot (in 2022) automatically configure the NTP as-it… but you can use this trick to fake it, by automatically creating a new connection-specific NTP configuration every time the connection changes and restarting <code>systemd-timesyncd.service</code>:		<li> '''Network Manager''' If you use Network Manager, then Network Manager cannot (in 2022) automatically configure the NTP as-it… but you can use this trick to fake it, by automatically creating a new connection-specific NTP configuration every time the connection changes and restarting <code>systemd-timesyncd.service</code>:

	<syntaxHighlight lang=nix>		<syntaxHighlight lang=nix>
Line 123:		Line 124:
	</syntaxHighlight>		</syntaxHighlight>
	You might need to wait a one or two minutes as <code>systemd-timesyncd</code> may try to load other ntp servers, timeout, and then try the new NTP server.		You might need to wait a one or two minutes as <code>systemd-timesyncd</code> may try to load other ntp servers, timeout, and then try the new NTP server.
			</li>
			</ol>

imported>Tobias.bora at 23:50, 22 November 2022

2022-11-22T23:50:25Z

← Older revision		Revision as of 23:50, 22 November 2022
Line 59:		Line 59:
	The procedure depends on how you configure internet. By default (if you have not installed network manager…) the [https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/tasks/network-interfaces-scripted.nix module <code>network-interfaces-scripted</code>] will be used… unfortunately as far as I know this script cannot deal with NTP.		The procedure depends on how you configure internet. By default (if you have not installed network manager…) the [https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/tasks/network-interfaces-scripted.nix module <code>network-interfaces-scripted</code>] will be used… unfortunately as far as I know this script cannot deal with NTP.

	If you use <code>systemd-networkd</code>, then it should automatically use the right NTP… However if you want the configuration to be automatic you want to use <code>networking.useNetworkd = true;</code> instead of <code>systemd.network.enable</code> (~~this last option requires further configuration~~), ~~and~~ <code>networking.useNetworkd</code> is apparently experimental now (2022) according to its documentation. As far as I understand you can also '''disable''' the default behavior using:		If you use <code>systemd-networkd</code>, then it should automatically use the right NTP… However if you want the configuration to be automatic you want to use <code>networking.useNetworkd = true;</code> instead of <code>systemd.network.enable</code> (<code>useNetworkd</code> will automatically configure <code>systemd.network</code> to provide a good default experience as alone <code>systemd.network</code> does basically nothing). However, <code>networking.useNetworkd</code> is apparently experimental now (2022) according to its documentation, so use it at your own risks. As far as I understand you can also '''disable''' the default behavior using:
	<syntaxHighlight lang=nix>		<syntaxHighlight lang=nix>
	systemd.network.config = {		systemd.network.config = {

imported>Tobias.bora at 23:30, 22 November 2022

2022-11-22T23:30:40Z

← Older revision		Revision as of 23:30, 22 November 2022
Line 59:		Line 59:
	The procedure depends on how you configure internet. By default (if you have not installed network manager…) the [https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/tasks/network-interfaces-scripted.nix module <code>network-interfaces-scripted</code>] will be used… unfortunately as far as I know this script cannot deal with NTP.		The procedure depends on how you configure internet. By default (if you have not installed network manager…) the [https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/tasks/network-interfaces-scripted.nix module <code>network-interfaces-scripted</code>] will be used… unfortunately as far as I know this script cannot deal with NTP.

	If you use <code>systemd-networkd</code>, then it should automatically use the right NTP… However if you want the configuration to be automatic you want to use <code>networking.useNetworkd = true;</code> instead of <code>systemd.network.enable</code> (this last option requires further configuration), and <code>networking.useNetworkd</code> is apparently experimental now (2022) according to its documentation.		If you use <code>systemd-networkd</code>, then it should automatically use the right NTP… However if you want the configuration to be automatic you want to use <code>networking.useNetworkd = true;</code> instead of <code>systemd.network.enable</code> (this last option requires further configuration), and <code>networking.useNetworkd</code> is apparently experimental now (2022) according to its documentation. As far as I understand you can also '''disable''' the default behavior using:
			<syntaxHighlight lang=nix>
			systemd.network.config = {
			dhcpV4Config = { UseNTP = false; };
			dhcpV6Config = { UseNTP = false; };
			}
			</syntaxHighlight>
			but I have not tested it.

	If you use Network Manager, then Network Manager cannot (in 2022) automatically configure the NTP as-it… but you can use this trick to fake it, by automatically creating a new connection-specific NTP configuration every time the connection changes and restarting <code>systemd-timesyncd.service</code>:		If you use Network Manager, then Network Manager cannot (in 2022) automatically configure the NTP as-it… but you can use this trick to fake it, by automatically creating a new connection-specific NTP configuration every time the connection changes and restarting <code>systemd-timesyncd.service</code>:

imported>Tobias.bora: NTP and DHCP

2022-11-22T23:26:47Z

NTP and DHCP

← Older revision		Revision as of 23:26, 22 November 2022
Line 21:		Line 21:
	* for '''openntpd''', use <code>services.openntpd.enable = true;</code>		* for '''openntpd''', use <code>services.openntpd.enable = true;</code>
	* for '''chrony''', use <code>services.chrony.enable = true;</code>		* for '''chrony''', use <code>services.chrony.enable = true;</code>

			== Set NTP from DHCP servers ==

			Most of the time the default NTP servers will be reachable. However, sometimes the NTP servers can be blocked by the firewall (for instance most universities block NTP for security reasons). This will be visible in the <code>systemd-timesyncd.service</code>:
			<syntaxHighlight>
			$ sudo systemctl status systemd-timesyncd.service
			● systemd-timesyncd.service - Network Time Synchronization
			…
			nov. 22 16:33:23 me systemd-timesyncd[2171]: Timed out waiting for reply from 94.198.159.11:123 (1.nixos.pool.ntp.org).
			…
			</syntaxHighlight>

			You can also test a specific server as follows:
			<syntaxHighlight>
			$ nix-shell -p ntp
			$ ntpdate -q 0.nixos.pool.ntp.org
			22 Nov 17:06:57 ntpdate[4020886]: no server suitable for synchronization found
			</syntaxHighlight>

			However, a replacement NTP is usually provided in that case via the DHCP protocol. You can see it for instance if you use Network Manager:
			<syntaxHighlight>
			$ nmcli connection show 'name-of-the-current-connection' \| grep ntp
			DHCP4.OPTION[8]: ntp_servers = 192.168.x.y
			DHCP4.OPTION[18]: requested_ntp_servers = 1
			$ ntpdate -q 192.168.x.y
			server 192.168.x.y, stratum 3, offset +2.493988, delay 0.02779
			22 Nov 16:51:37 ntpdate[3923570]: step time server 192.168.128.1 offset +2.493988 sec
			</syntaxHighlight>

			You might also be able to get the actual hostname of the DHCP (if it exists) using:
			<syntaxHighlight>
			$ sudo nmap -sP 192.168.x.y
			</syntaxHighlight>

			Then, you can of course manually add the DHCP server as explained above… but it's not practical when you often go to new places, or if the NTP server changes over time. For laptop it may not be a big issue (your internal clock will be used in that case until you reach a new network without firewalls) but for some devices like raspberry pi that can't store the time when device is turned off, or for servers that will always be behind the firewall, it can be interesting to automatically configure the NTP server using DHCP.

			The procedure depends on how you configure internet. By default (if you have not installed network manager…) the [https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/tasks/network-interfaces-scripted.nix module <code>network-interfaces-scripted</code>] will be used… unfortunately as far as I know this script cannot deal with NTP.

			If you use <code>systemd-networkd</code>, then it should automatically use the right NTP… However if you want the configuration to be automatic you want to use <code>networking.useNetworkd = true;</code> instead of <code>systemd.network.enable</code> (this last option requires further configuration), and <code>networking.useNetworkd</code> is apparently experimental now (2022) according to its documentation.

			If you use Network Manager, then Network Manager cannot (in 2022) automatically configure the NTP as-it… but you can use this trick to fake it, by automatically creating a new connection-specific NTP configuration every time the connection changes and restarting <code>systemd-timesyncd.service</code>:

			<syntaxHighlight lang=nix>
			# In /etc/nixos/configuration.nix
			{ pkgs, lib, options, ...}
			{
			## To use, put this in your configuration, switch to it, and restart NM:
			## $ sudo systemctl restart NetworkManager.service
			## To check if it works, you can do `sudo systemctl status systemd-timesyncd.service`
			## (it may take a bit of time to pick the right NTP as it may try the
			## other NTP firsts)
			networking.networkmanager.dispatcherScripts = [
			{
			# https://wiki.archlinux.org/title/NetworkManager#Dynamically_set_NTP_servers_received_via_DHCP_with_systemd-timesyncd
			# You can debug with sudo journalctl -u NetworkManager-dispatcher -e
			# make sure to restart NM as described above
			source = pkgs.writeText "10-update-timesyncd" ''
			[ -z "$CONNECTION_UUID" ] && exit 0
			INTERFACE="$1"
			ACTION="$2"
			case $ACTION in
			up \| dhcp4-change \| dhcp6-change)
			systemctl restart systemd-timesyncd.service
			if [ -n "$DHCP4_NTP_SERVERS" ]; then
			echo "Will add the ntp server $DHCP4_NTP_SERVERS"
			else
			echo "No DHCP4 NTP available."
			exit 0
			fi
			mkdir -p /etc/systemd/timesyncd.conf.d
			# <<-EOF must really use tabs to keep indentation correct… and tabs are often converted to space in wiki
			# so I don't want to risk strange issues with indentation
			echo "[Time]" > "/etc/systemd/timesyncd.conf.d/''${CONNECTION_UUID}.conf"
			echo "NTP=$DHCP4_NTP_SERVERS" >> "/etc/systemd/timesyncd.conf.d/''${CONNECTION_UUID}.conf"
			systemctl restart systemd-timesyncd.service
			;;
			down)
			rm -f "/etc/systemd/timesyncd.conf.d/''${CONNECTION_UUID}.conf"
			systemctl restart systemd-timesyncd.service
			;;
			esac
			echo 'Done!'
			'';
			}
			];
			}
			</syntaxHighlight>

			To apply the change, switch to your new configuration and make sure to restart Network Manager:
			<syntaxHighlight lang=nix>
			$ sudo systemctl restart NetworkManager.service
			# Check if the NTP server is used (may need to wait a few minutes)
			$ sudo systemctl status systemd-timesyncd.service
			</syntaxHighlight>
			You might need to wait a one or two minutes as <code>systemd-timesyncd</code> may try to load other ntp servers, timeout, and then try the new NTP server.

imported>Symphorien: mention a trick to get the default value of an option, applied to ntp servers.

2018-09-10T18:30:12Z

mention a trick to get the default value of an option, applied to ntp servers.

New page

[https://en.wikipedia.org/wiki/Network_Time_Protocol NTP] is a protocol to synchronise time and date information through a network. It is used to set the clock of your system automatically when your computer is connected to the internet.

== NTP servers ==

To choose which servers to ask for time information to, use the <code>networking.timeServers</code> option.
If you simply want to ''add'' a server to the default list, you can retrieve the default value of the option under the name <code>options.networking.timeServers.default</code>. Make sure to have <code>options</code> in the arguments at the beginning of the file:
{{file|/etc/nixos/configuration.nix|nix|<nowiki>
{ pkgs, lib, options, ...}
{
networking.timeServers = options.networking.timeServers.default ++ [ "ntp.example.com" ];
}
</nowiki>}}
{{Evaluate}}

== NTP daemon ==

Different NTP daemons are available on NixOS. The default one is <code>systemd-timesyncd</code>. To switch to another
implementation:
* for '''ntpd''', use <code>services.ntp.enable = true;</code>
* for '''openntpd''', use <code>services.openntpd.enable = true;</code>
* for '''chrony''', use <code>services.chrony.enable = true;</code>