Set write permissions for www-data + dummy_user?

Question

Nginx

there is root (by which you cannot enter) and std. user. dummy_user
The problem is that if www-data creates a file, dummy_user can't write to it and can do the opposite.
I even tried to make a folder 777, it did not help. Folder owner - dummy_user.

Answer 1

sudo adduser dummy_user <имя_группы>
group_name is most likely www-data, like the www-data user
in general, you need to make them members of the same group

Answer 2

Add them to one group and give this group rights to the folder with files.