Update page '6-9-2023 Cohort 1 Sync Notes'

6-9-2023 Cohort 1 Sync Notes.md

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+1433h Started
+* Code review
+* NTP was selected for time synchronization: see https://gogs.gtsplab.com:5432/SVIG/pricer/src/9af1def1d0a6365fe0cdfe639afa681654b38533/fp2_14.py#L261
+* Links to source code files should use the "permalink" button to reference a specific revision, or the line numbers you're referencing will quickly become wrong.
+* Windows time infrastructure: https://learn.microsoft.com/en-us/windows-server/networking/windows-time-service/windows-time-service-tools-and-settings?tabs=config
+* MacOS time infrastructure: https://keith.github.io/xcode-man-pages/timed.8.html (every 20 minutes)
+* Functional vs non-functional requirements (<= 9.1 hours) https://learn.microsoft.com/en-us/troubleshoot/windows-server/identity/specialpollinterval-polling-interval-time-service-not-correct
+* https://en.wikipedia.org/wiki/Non-functional_requirement
+* Filesystems can't express times with finer granularity than 1ms
+* Error in terms of time synchronization is expressed in ppm (1 microsecond) or ppb (1 nanosecond)
+* Therefore, there's no advantage to synchronizing to less than 1000ppm.
+* Windows resync command: 
+```powershell
+Start-Service W32Time
+w32tm /resync
+```
+* MacOS resync command: TODO @j
+* Use `platform.system()` to figure out whether it's Windows or MacOS, and use `subprocess` to run the NTP sync command so the whole computer has accurate time.  Make sure to check the return code (0 = success, not zero = failure)
+* Although `subprocess` can give you the return code directly, it's helpful to know that it's available in the shell/powershell as `$?` on MacOS/Linux, and `$LASTEXITCODE` in powershell.
+* TODO @j figure out how to get systemd running in the container
+1515h: Ended