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|description=A reasonably accurate host clock is required for many general security properties. An inaccurate clock can lead to broken internet connectivity and time related security issues.
|image=TineSynchronization2134234.jpg
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{{intro|
A reasonably accurate host clock is required for many general security properties. An inaccurate clock can lead to broken internet connectivity and time related security issues.
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= Introduction =

It is recommended to have a host clock with accuracy of up to ± 30 minutes. Clocks that are days, weeks, months or even years slow or fast can lead to many issues such as connectivity problems with Tor, inability to download operating system upgrades. <ref>
Due to invalid (not yet or no longer valid) TLS certificates.
</ref>

Follow the platform-specific recommendations below to avoid Tor connectivity problems and to limit possible adverse security impacts.

= All Platforms =

If the host clock is more than 1 hour in the past or more than 3 hours in the future, Tor cannot connect. In this case, manually fix the host clock by right-clicking on it, and also check for an empty battery.

* If using {{project_name_long}} as a host operating system: Reboot. (Easiest.)
* If using a VM: Then, power off and power on {{project_name_gateway_long}} and Tor should be able to reconnect.
* Due to [[Network_Time_Synchronization#Block_Networking_until_sdwdate_Finishes|Block Networking until sdwdate Finishes]] if Tor failed or took too long to connect, then you need to fix Tor connection first and then restart your sdwdate <code>sudo systemctl restart sdwdate</code> in your VM/Qube.

= Easy instructions =
<u>{{non_q_project_name_short}} in VMs or as a host operating system:</u> It is strongly discouraged to use the pause / suspend / save / hibernate features.

<u>{{q_project_name_long}} VMs:</u> It is strongly discouraged to use the pause feature of Qube Manager, but it is is safe to use the suspend or hibernate feature of dom0.

= Advanced instructions =

<div class="toccolours mw-collapsible mw-collapsed">
If you are interested in using the pause / suspend / save / hibernate features, please click the expand button for further instructions.
<div class="mw-collapsible-content">

'''<u>{{project_name_workstation_long}} as a host operating system or VM</u>''':

* It is strongly discouraged to pause / suspend / save / hibernate {{project_name_short}}. If this advice is ignored, [[#Restart sdwdate|restart sdwdate]] after resume. <ref>
Similarly, if users suspend or save the {{project_name_workstation_short}} state, the clock will again lag behind the correct value. This can be manually fixed by running: <code>Start Menu</code> &rarr; <code>Applications</code> &rarr; <code>System</code> &rarr; <code>Time Synchronization Monitor (sdwdate-gui)</code> &rarr; <code>restart sdwdate</code>.
</ref>

'''<u>{{q_project_name_short}}</u>''':

* <u>VM</u>: It is strongly discouraged to pause {{project_name_workstation_short}} VMs using the pause feature of Qube Manager. If this advice is ignored, [[#Restart sdwdate|restart sdwdate]] after resume. <ref>
Qubes does not dispatch the <code>/etc/qubes/suspend-post.d</code> / <code>/etc/qubes/suspend-pre.d</code> hooks upon pause / resume using Qube Manager.
</ref>
* <u>dom0 suspend / hibernate</u>: It is safe to use the suspend or hibernate feature of dom0 and a manual restart of sdwdate is unnecessary. <ref>
https://github.com/QubesOS/qubes-issues/issues/1764
</ref>
</div>
</div>

= Restart sdwdate =
To restart <code>sdwdate</code>.

<code>Start Menu</code> &rarr; <code>Applications</code> &rarr; <code>System</code> &rarr; <code>Time Synchronization Monitor (sdwdate-gui)</code> &rarr; <code>restart sdwdate</code>

Or in a terminal. <ref>
Simplified in next upgrade.

{{CodeSelect|code=
sudo sdwdate-clock-jump
}}
</ref>

{{CodeSelect|code=
sudo /usr/lib/sdwdate/restart_fresh
}}

= Manually Set Clock Time and Date =
Usually not required.

In case [[Sdwdate|sdwdate]] fails to properly randomize the system clock, it is possible to manually set a random value.

The first step should be completed on the host to ensure the host clock is set to the correct time.
{{Box|text=
'''1.''' On the host ([[Qubes|{{q_project_name_short}}]]: <code>dom0</code>), run the following command to report the time in UTC.

{{CodeSelect|code=
date -u
}}

The output should be similar to the following. <ref>
{{CodeSelect|code=
Mon Apr 22 04:30:44 UTC 2019
}}
</ref>

{{CodeSelect|code=
{{CURRENTMONTHABBREV}} {{CURRENTDAY2}} {{CURRENTTIME}}:44 UTC {{CURRENTYEAR}}
}}

'''2.''' Set the correct time in {{project_name_gateway_short}}.

Run the following command with the correct date and time parameters. <ref>
A non-zero exit codes signifies an error, while <code>0</code> means it succeeded.
</ref> <ref>
Also see:

{{CodeSelect|code=
man clock-random-manual-gui
}}

{{CodeSelect|code=
man clock-random-manual-cli
}}
</ref>

* <code>clock-random-manual-gui</code>: a randomized clock setting (in UTC) is entered via a GUI.
* <code>clock-random-manual-cli</code>: a randomized clock setting (in UTC) is entered on the command line. For example <ref>
{{CodeSelect|code=
echo "Sat Oct 26 07:18:25 UTC 2019" {{!}} /usr/bin/clock-random-manual-cli
}}
</ref>:
{{CodeSelect|code=
echo "{{CURRENTMONTHABBREV}} {{CURRENTDAY2}} {{CURRENTTIME}}:44 UTC {{CURRENTYEAR}}" {{!}} sudo clock-random-manual-cli
}}

'''3.''' Restart sdwdate.

{{CodeSelect|code=
sudo service sdwdate restart
}}

'''4.''' If Tor is still not functional, try restarting Tor.

{{CodeSelect|code=
sudo service tor restart
}}

Tor should work once correct clock values are set, but that can be manually tested with [[systemcheck]].
}}

= Block Networking until sdwdate Finishes =

[[Sdwdate|sdwdate]] is a Tor-friendly replacement for rdate and ntpdate that sets the system's clock by communicating via end-to-end encrypted TCP with Tor onion webservers. Since timekeeping is crucial for security, blocking network access until sdwdate succeeds is sensible. <ref>
https://forums.whonix.org/t/blocking-networking-until-sdwdate-finished/5372
</ref>

Note: When using this feature, there will be no internet connectivity until sdwdate succeeded which could take approximately 2 minutes.

How to enable this feature? [[Unsupported]]. This feature is has not been implemented yet for {{project_name_short}}. Developers are welcome to contribute to {{project_name_short}}.

= Summary =

'''Table:''' ''Network Time Synchonization Summary''

{| class="wikitable"
|-
! scope="col"| '''Platform'''
! scope="col"| '''Recommendations'''
|-
! scope="row"| All Platforms
|
* Tor cannot connect if the host clock is grossly inaccurate. In this case, users should manually fix the host clock before powering the {{project_name_gateway_short}} off and on again.
* Periodically check the host clock to ensure that it is accurate or approximately so.
* For greater security, [[#Block_Networking_until_sdwdate_Finishes|block networking until sdwdate finishes]].
|-
! scope="row"| {{non_q_project_name_short}}
|
* It is strongly discouraged to use the pause / suspend / save / hibernate features.
|-
! scope="row"| {{q_project_name_short}}
|
* It is strongly discouraged to use the pause feature of Qube Manager.
* it is is safe to use the suspend or hibernate feature of dom0.
|}

= Appendix =

== Deactivate Automatic TimeSync ==

{{mbox
| image   = [[File:Ambox_warning_pn.svg.png|40px]]
| text    =
'''Warning:''' This action is recommended against and is usually not required. In all cases, first check with the {{project_name_short}} developers.
}}

To deactivate sdwdate, run.

{{CodeSelect|code=
sudo service sdwdate stop
}}

{{CodeSelect|code=
sudo systemctl mask sdwdate
}}

= Related =
* [[Timezone]]
* [[sdwdate]]
* [[sdwdate-gui]]
* [[Boot Clock Randomization]]
* [[Time Attacks]]
* [[Dev/sdwdate]]
* [[Dev/TimeSync]]

= Footnotes =
{{reflist|close=1}}

{{Footer}}

[[Category:Documentation]]