How to register or renew the Let’s Encrypt certificate on Synology DSM 6.2.3 and below

Problem

https://kb.synology.com/en-vn/DSM/tutorial/What_should_I_do_if_cannot_add_renew_lets_encrypt

The Let’s Encrypt DST Root CA X3 certificate has been expired since September 30, 2021 (details). For DSM 6.2.3 and below, you must update to at least DSM 6.2.4 Update 2 to obtain a Let’s Encrypt certificate.

Solution

Connect to DSM via SSH

$ sudo -s
$ cp /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/ca-certificates.crt.ORIG
$ curl -k “https://letsencrypt.org/certs/isrgrootx1.pem" >> /etc/ssl/certs/ca-certificates.crt
$ reboot

Let’s try to renew the Let’s Encrypt certificates on DSM UI