I use Virtualmin’s built in cron job editor under “Webmin” >> “System” >> “Scheduled Cron Jobs” and created a new cron job with these settings:
Run at 5:47 and 17:47 every day (runs twice a day around quarter 6 in the morning and evening). I selected minute 47 because a lot of people will select on the hour, so 47 minutes passed will result in a lower probability of not being able to connect to the Letsencrpt server. It’s like everyone getting up on a ad break to make a cup of tea, there’s a surge of users :-)
Don’t use 47 minutes past AND 5 and 17 hours like I have, use another minute (like 33 or 52 or 27) and different hours (like 3 and 15, or 1 and 13, or 9 and 21). This will setup a cron job to run every 12 hour, but at different times for each user (this spreads the load on the Letsencrypt server: if everyone uses the same time their server could crash!).
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