prokurator

I already mentioned that mod rewrite works just fine on single installed WP.
Secondly, all I have is on Ubuntu 16.04

Thank you

No, this is not the problem. mod rewrite is installed and works properly. I have single WordPress installation along side with multi one and single works just fine and properly displays posts and pages.

Thanks, but this is slightly different than what I am looking for. I want force new user to register with email address as username to be used as user_login value in users table.

Thanks to everybody. Honestly, I understood most of ti from the beginning. What I was confused with is specifically for text files. I uploaded jst one to test. I know if I will click on send to editor it will be available in the post. But does it mean ‘linked to file/page’ I did not get.

Just to let you know, that server where I test WordPress does not have ImageMagick. I could not test thumbnail creation. But I know it works. I tested it before on another server.

Thanks.

It is not defined there. You can find function get_posts() and get_postdata(). But there is no get_post()

I just uploaded latest version of wordpress 1.5.1.3

there is mistyped name of the function. Line 224 should be like this:
$postdata = &get_postdata($post_ID);