How to tell the ubunty server through the console to respond, for a specific domain, with a 503 error?

Question

Command line

I enter the command into the console, and when I go to site.ru I get an error 503, I enter the cancel command and go back to the site and the site works fine.
How can this be checked?

Answer 1

using echo to make changes to the config https://losst.ru/komanda-echo-v-linux