The original protocol used by Let's Encrypt for certificate issuance and management is called ACMEv1. In March of 2018 we introduced support for ACMEv2, a newer version of the protocol that matches what was finalized today as RFC 8555 362. Let's Encrypt have been encouraging subscribers to move to the ACMEv2 protocol.
In November of 2019 Let's Encrypt stop allowing new account registrations through our ACMEv1 API endpoint. Existing accounts will continue to function normally.
很多虛擬主機使用開放原始碼webmin管理軟體進行維運，webmin管理介面當中提供免費SSL安全憑證申請功能。在2019年11月起有許多管理員遇到更新問題，錯誤訊息告知upgrade your ACME client，針對問題，我們進行本篇網頁文章撰寫，如果有解決您的問題，本頁有使用臉書API，請幫我們按讚喔!!
yum install certbot或
yum install letsencryptcertbot的別名是letsencrypt，它們是同一個軟體包裝。
certbot register --email firstname.lastname@example.org --agree-tos
在我們使用免費SSL憑證時也應該要感謝一下certbot的專案維運單位Electronic Frontier Foundation
The Electronic Frontier Foundation is the leading organization protecting civil liberties in the digital world. Founded in 1990, we defend free speech online, fight illegal surveillance, promote the rights of digital innovators, and work to ensure that the rights and freedoms we enjoy are enhanced, rather than eroded, as our use of technology grows. EFF is a member-supported organization. Find out more at https://eff.org.
Certbot is part of a growing number of EFF technology projects designed to protect your online freedom. EFF helped develop Let’s Encrypt, the free SSL certificate authority expanding the availability of encryption and taking the web by storm. We created HTTPS Everywhere to help ensure that users connect to websites securely. We also maintain Privacy Badger, a free browser tool that helps hundreds of thousands of Internet users block third-party scripts and cookies that track users across the web. EFF works on the side of ordinary users and advanced developers alike because together, we can build a safer, more privacy-friendly web.