Did you click on and follow the instructions from the link in the phrase “First you’ll have to follow the instructions here to enable the Jessie backports repo (…)”? You’ll notice the word “here” is a link to click on. (On the instruction page, not in my post…)
i’ve run apt-get update again and now it works i think it’s fine now thank you i can execute the other comand lines but i have another problem i dont understand why i have this
The following errors were reported by the server:
Detail: Incorrect validation certificate for tls-sni-01 challenge.
from 18.104.22.168:443. Received 1 certificate(s), first
certificate had names “meet.mezalab.fr”
To fix these errors, please make sure that your domain name was
entered correctly and the DNS A record(s) for that domain
contain(s) the right IP address.