Our servers went through a few major system changes during the years:

  • upgrade from Ubuntu 16.04
  • update to python 3
  • modules deployed for instrumentation and monitoring

and as a result different packages were not renewed automatically. One of them was the certbot application from Let’s Encrypt.Today we realized the auto update feature was failing. I logged in and tried a dry run, the result is shown below.

The error is a module named _cffi_backend. After a few google searches it seemed there were packages missing from certbot / python3 application.

This is what worked for us:

  • python3 -m pip install cffi
  • python3 -m pip install certbot-nginx

then we checked the installation with a dry run

  • sudo certbot renew –dry-run

The certificates were renewed and hopefully the next renewal will be without hiccups.


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