How can I avoid repeating DocumentRoot in this Apache virtual host?

Question

I have an Apache virtual host configured for a website powered by Wordpress.

<VirtualHost *:80>
ServerName 67.178.132.253
DocumentRoot /home/david/wordpressWebsite

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteRule ^index\.php$ - [L]
RewriteCond /home/david/wordpressWebsite%{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress

</VirtualHost>

How can I avoid hard-coding /home/david/wordpressWebsite twice? I don't want to use REQUEST_URI since that involves an extra request.

Here's my attempt at using a directory context. I made a file in sites-available with these contents.

DocumentRoot /home/david/wordpressWebsite

<Directory /home/david/wordpressWebsite>
    RewriteEngine On
    RewriteRule ^index\.php$ - [L]
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteRule . index.php [L]
    # You need these somewhere, anyway; better to not put them on the root.
    Order allow,deny
    Allow from all
</Directory>

For some reason, Apache is seeking files in /var/www as evinced in my error logs:

[error] [client 69.175.67.64] File does not exist: /var/www/about, 
referer: http://67.178.132.253/

Answer 1

For future people who stumble upon this and want an answer to the original question:
How can I avoid repeating DocumentRoot in this Apache virtual host?

The value of the DocumentRoot directive can be accessed by using the server variable
%{DOCUMENT_ROOT}. This means that in the OPs example, instead of writing:

RewriteCond /home/david/wordpressWebsite%{REQUEST_FILENAME} !-f

We can write

RewriteCond %{DOCUMENT_ROOT}%{REQUEST_FILENAME} !-f

Therefore, the only place you should hard code your root file path is in the DocumentRoot directive.

Answer 2

Those Wordpress rules were built to be inside a <Directory> context, as evidenced by the fact that they're looking for ^index\.php$ without a leading slash; that rule won't ever match in a <VirtualHost> context.

Once inside a <Directory> context, the REQUEST_FILENAME variable contains the physical file location, as explain in the documentation:

The full local filesystem path to the file or script matching the request, if this has already been determined by the server at the time REQUEST_FILENAME is referenced. Otherwise, such as when used in virtual host context, the same value as REQUEST_URI.

So, try something like this:

<Directory /home/david/wordpressWebsite>
    RewriteEngine On
    RewriteRule ^index\.php$ - [L]
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteRule . index.php [L]
    # You need these somewhere, anyway; better to not put them on the root.
    Order allow,deny
    Allow from all
</Directory>

As far as hard-coding it twice (in both the DocumentRoot and <Directory> settings): if you really need to avoid that for some reason, then look into the "config file variables" feature of Apache 2.4.