As per the title, I have to create a file, for example:

```
/home/john/file.ini

```

I created a user and a group, `myuser` and `mygroup`, and set them to be the owner and group of this `file.ini`:

```
chown myuser:mygroup file.ini

```

I have another user named `mymain`. This user must be able to read this file. How can I change the permissions to allow this?

**Important: I want to allow only the "mymain" user to read this file, NOT all other users.**

So myuser (the owner of the file) and mymain should have access.