LetsEncrypt auto renew in Webmin

Ilia · June 5, 2026, 10:27pm

Ugh, gosh! You’re right—there was a bug. It’s really surprising how long it was there! Thanks for the tip! Fixed in this PR:

github.com/webmin/webmin

Fix LE renewal to schedule by elapsed interval (#2752)

master ← dev/fix-broken-renewals

opened 10:24PM - 05 Jun 26 UTC

iliaross

+34 -8

Howdy, Jamie! This turned out to be a bug after [this](https://forum.virtualmin….com/t/letsencrypt-auto-renew-in-webmin/137371/12?u=ilia) comment on the Virtualmin forum. The Webmin SSL LE renewal setting is labeled as "Months between automatic renewal", but it was previously saved as a calendar-style cron month expression like `*/N`. That is not the same as an elapsed renewal interval. Webmin’s cron matcher evaluates month schedules against calendar month numbers, so values like `*/5`, `*/12`, or values above `12` do not reliably mean “renew every N months”. This could cause uneven or dangerously late renewal timing. This changes the renewal job to use Webmin cron’s elapsed `interval` support instead of calendar-month matching. - Saves automatic renewal as `renew * 30 * 24 * 60 * 60` seconds. - Clears the cron time fields so the scheduler uses the interval path only. - Keeps `months => '*/N'` so the SSL UI can continue to display the saved renewal value. - Resets the renewal timer only after a newly issued certificate. - Preserves the existing renewal timer for settings-only saves. - Migrates existing month-based Let's Encrypt renewal jobs during postinstall.