vi /etc/crontab 추가
10 */6  * * *  root    certbot -auto renew --renew-hook "service apache2 restart"

인증서 상태 보기
# certbot -auto certificates

Saving debug log to /var/log/letsencrypt/letsencrypt.log
-------------------------------------------------------------------------------
Found the following certs:
  Certificate Name: *****
    Domains: *****
    Expiry Date: 2018-03-30 10:06:03+00:00 (VALID: 39 days)
    Certificate Path: /etc/letsencrypt/live/*****/fullchain.pem
    Private Key Path: /etc/letsencrypt/live/*****/privkey.pem
-------------------------------------------------------------------------------



수동갱신하기 (만료 날짜가 되면 동작된다.)

# certbot -auto renew
Saving debug log to /var/log/letsencrypt/letsencrypt.log
-------------------------------------------------------------------------------
Processing /etc/letsencrypt/renewal/*****.conf
-------------------------------------------------------------------------------
Cert not yet due for renewal
-------------------------------------------------------------------------------
The following certs are not due for renewal yet:
  /etc/letsencrypt/live/*****/fullchain.pem (skipped)
No renewals were attempted.
-------------------------------------------------------------------------------

출처 : howcode.co.kr  로빈아빠 김성대