When working with Apache2 web server on Ubuntu Linux, we often need to serve different content from separate directories under the same domain. This is particularly useful when you want to maintain modular applications or separate different sections of your website while keeping everything under a single domain.

In this scenario, we have:

/srv/www/blog/      # Blog content
/srv/www/mainsite/  # Primary website content

The solution involves using Apache's Alias directive and Directory blocks rather than separate virtual hosts. Here's a complete configuration example for your /etc/apache2/sites-available/000-default.conf or a new configuration file:

<VirtualHost *:80>
    ServerName mysite.com
    DocumentRoot /srv/www/mainsite

    Alias /blog /srv/www/blog
    
    <Directory /srv/www/mainsite>
        Options Indexes FollowSymLinks
        AllowOverride All
        Require all granted
    </Directory>
    
    <Directory /srv/www/blog>
        Options Indexes FollowSymLinks
        AllowOverride All
        Require all granted
    </Directory>
    
    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined
</VirtualHost>

After creating or modifying your configuration file:

sudo a2ensite your-config-file.conf
sudo systemctl reload apache2

For more complex scenarios, you might want to consider:

# Example of additional directives you might need
<Location /blog>
    SetEnv BLOG_MODE production
    Header set X-Blog-Version "2.0"
</Location>

If you encounter permission issues, ensure:

sudo chown -R www-data:www-data /srv/www
sudo chmod -R 755 /srv/www

Check Apache error logs for detailed debugging:

tail -f /var/log/apache2/error.log

For better performance with multiple directories:

# Enable content caching
<IfModule mod_cache.c>
    CacheQuickHandler on
    CacheLock on
    CacheLockPath /tmp/mod_cache-lock
    CacheLockMaxAge 5
    CacheIgnoreCacheControl On
    CacheIgnoreNoLastMod On
    CacheStoreNoStore On
    CacheStorePrivate On
</IfModule>

When working with Apache2 on Ubuntu Linux, you might need to serve multiple websites from different directories under the same domain. This is particularly common when:

• Hosting a blog as a subdirectory of your main site
• Serving different applications under the same domain
• Maintaining separate codebases for different site sections

Instead of using separate virtual hosts (which typically require different domains or IPs), we'll use Apache's Alias directive and Directory settings:

<VirtualHost *:80>
    ServerName mysite.com
    DocumentRoot /srv/www/mainsite
    
    Alias /blog /srv/www/blog
    <Directory "/srv/www/blog">
        Options Indexes FollowSymLinks
        AllowOverride All
        Require all granted
    </Directory>
    
    <Directory "/srv/www/mainsite">
        Options Indexes FollowSymLinks
        AllowOverride All
        Require all granted
    </Directory>
</VirtualHost>

1. Create a new configuration file:

sudo nano /etc/apache2/sites-available/mysite.conf

2. Paste the configuration above, adjusting paths as needed

3. Enable the site and restart Apache:

sudo a2ensite mysite.conf
sudo systemctl restart apache2

For more complex scenarios, you might need additional directives:

# For PHP applications:
<FilesMatch \.php$>
    SetHandler application/x-httpd-php
</FilesMatch>

# Custom error documents:
ErrorDocument 404 /errors/404.html

# URL rewriting:
RewriteEngine On
RewriteRule ^blog/old/(.*)$ /blog/new/$1 [R=301,L]

If you encounter problems:

• Check Apache error logs: tail -f /var/log/apache2/error.log
• Verify file permissions: sudo chown -R www-data:www-data /srv/www
• Test configuration: sudo apache2ctl configtest

When serving multiple directories:

• Enable caching for static assets
• Consider using mod_deflate for compression
• Implement proper .htaccess rules to avoid performance hits