Thanks, the instructions are very clear and detailed. I did the following, but still required 2-factor authentication when logging in. Do not know where is wrong?
root@hoi-dap:/var/discourse# ./launcher enter app
root@hoi-dap-app:/var/www/discourse# rails c
[1] pry(main)> SiteSetting.enforce_second_factor='no'
=> "no"
[2] pry(main)> exit
root@hoi-dap-app:/var/www/discourse# exit
logout