Ja genau, eine Multisite-Installation mit einer .htaccess.
Das CMS ist prinzipiell für Multi-Sites geeignet. Pro Domain wird ein Seitenbaum angelegt, in dem jeweils in den DNS Einstellungen die Domain eingetragen wird, unter der der Seitenbaum erreichbar ist. Das funktioniert auch, solange ich nicht die URL-Umschreibung ohne Suffix einstelle. Ich hatte testweise die URL-Umschreibung mit dem Suffix .html eingestellt, da tritt dieses Phänomen nicht auf. Da gibt es dann korrekterweise einen 404, wenn ich von der Subdomain versuche, die Seiten der Hauptdomain aufzurufen. Die vollständiger .htaccess sieht so aus:
##
##
# Prevent access to the Contao template files
##
<FilesMatch "\.(tpl|html5|xhtml)$">
<IfModule !mod_authz_core.c>
Order deny,allow
Deny from all
</IfModule>
<IfModule mod_authz_core.c>
Require all denied
</IfModule>
</FilesMatch>
##
# Allow access from all domains for webfonts
# @see https://github.com/h5bp/html5-boilerplate
##
<IfModule mod_headers.c>
<FilesMatch "\.(ttf|ttc|otf|eot|woff2?|font\.css)$">
Header set Access-Control-Allow-Origin "*"
</FilesMatch>
</IfModule>
##
# Disable ETags
# @see http://developer.yahoo.com/performance/rules.html#etags
##
FileETag None
<IfModule mod_headers.c>
Header unset ETag
</IfModule>
##
# Set the proper MIME types
# @see https://github.com/h5bp/html5-boilerplate
##
<IfModule mod_mime.c>
AddType application/javascript js jsonp
AddType application/json json
AddType audio/ogg oga ogg
AddType audio/mp4 m4a f4a f4b
AddType video/ogg ogv
AddType video/mp4 mp4 m4v f4v f4p
AddType video/webm webm
AddType video/x-flv flv
AddType image/svg+xml svg svgz
AddEncoding gzip svgz
AddType application/vnd.ms-fontobject eot
AddType application/x-font-ttf ttf ttc
AddType font/opentype otf
AddType application/x-font-woff woff woff2
AddType image/x-icon ico
AddType image/webp webp
AddType text/cache-manifest appcache manifest
AddType text/x-component htc
AddType application/xml rss atom xml rdf
AddType application/x-web-app-manifest+json webapp
AddType text/x-vcard vcf
AddType application/x-shockwave-flash swf
</IfModule>
##
# Gzip compression
# @see https://github.com/h5bp/html5-boilerplate
##
<IfModule mod_deflate.c>
<IfModule mod_filter.c>
AddOutputFilterByType DEFLATE text/html text/plain text/css application/json
AddOutputFilterByType DEFLATE application/javascript
AddOutputFilterByType DEFLATE text/xml application/xml text/x-component
AddOutputFilterByType DEFLATE application/xhtml+xml application/rss+xml application/atom+xml
AddOutputFilterByType DEFLATE image/x-icon image/svg+xml application/vnd.ms-fontobject application/x-font-ttf font/opentype
</IfModule>
</IfModule>
##
# Expires headers (for better cache control)
# @see https://github.com/h5bp/html5-boilerplate
##
<IfModule mod_expires.c>
ExpiresActive on
##
# Productional website
##
ExpiresByType text/cache-manifest "access plus 0 seconds"
ExpiresByType text/html "access plus 0 seconds"
ExpiresByType text/xml "access plus 0 seconds"
ExpiresByType application/xml "access plus 0 seconds"
ExpiresByType application/json "access plus 0 seconds"
ExpiresByType application/rss+xml "access plus 1 hour"
ExpiresByType application/atom+xml "access plus 1 hour"
ExpiresByType image/gif "access plus 1 month"
ExpiresByType image/png "access plus 1 month"
ExpiresByType image/jpeg "access plus 1 month"
ExpiresByType image/x-icon "access plus 1 month"
ExpiresByType video/ogg "access plus 1 month"
ExpiresByType audio/ogg "access plus 1 month"
ExpiresByType video/mp4 "access plus 1 month"
ExpiresByType video/webm "access plus 1 month"
ExpiresByType text/x-component "access plus 1 month"
ExpiresByType application/x-font-ttf "access plus 1 month"
ExpiresByType font/opentype "access plus 1 month"
ExpiresByType application/x-font-woff "access plus 1 month"
ExpiresByType image/svg+xml "access plus 1 month"
ExpiresByType application/vnd.ms-fontobject "access plus 1 month"
ExpiresByType text/css "access plus 1 year"
ExpiresByType application/javascript "access plus 1 year"
##
# Disable caching during development
# @see https://github.com/contao/core/issues/4364
##
#ExpiresByType text/cache-manifest "access"
#ExpiresByType text/html "access"
#ExpiresByType text/xml "access"
#ExpiresByType application/xml "access"
#ExpiresByType application/json "access"
#ExpiresByType application/rss+xml "access"
#ExpiresByType application/atom+xml "access"
#ExpiresByType image/gif "access"
#ExpiresByType image/png "access"
#ExpiresByType image/jpeg "access"
#ExpiresByType image/x-icon "access"
#ExpiresByType video/ogg "access"
#ExpiresByType audio/ogg "access"
#ExpiresByType video/mp4 "access"
#ExpiresByType video/webm "access"
#ExpiresByType text/x-component "access"
#ExpiresByType application/x-font-ttf "access"
#ExpiresByType font/opentype "access"
#ExpiresByType application/x-font-woff "access"
#ExpiresByType image/svg+xml "access"
#ExpiresByType application/vnd.ms-fontobject "access"
#ExpiresByType text/css "access"
#ExpiresByType application/javascript "access"
</IfModule>
##
# Header adjustments
##
<IfModule mod_headers.c>
##
# Disable caching during development
# @see https://github.com/contao/core/issues/4364
##
#Header unset Cache-Control
#Header append Cache-Control must-revalidate
##
# Do not cache the cron.txt file
# @see https://github.com/contao/core/issues/5105
##
<FilesMatch "cron\.txt$">
Header set Cache-Control "no-cache, no-store, must-revalidate, max-age=0, proxy-revalidate, no-transform"
</FilesMatch>
##
# Add a Vary Accept-Encoding header for the compressed resources. If you
# modify the file types above, make sure to change them here accordingly.
# @see http://developer.yahoo.com/performance/rules.html#gzip
#
# Note: If you are using a case-sensitive file system like HFS+ or ext4, you
# have to change the <FilesMatch> directive as follows:
#
# <FilesMatch "\.(?i:js|css|xml|gz|svgz)$">
#
# For more information see: https://github.com/contao/core/issues/4364
##
<FilesMatch "\.(js|css|xml|gz|svgz)$">
Header append Vary Accept-Encoding
</FilesMatch>
</IfModule>
# Deflate Compression by FileType
# <IfModule mod_deflate.c>
# AddOutputFilterByType DEFLATE text/plain
# AddOutputFilterByType DEFLATE text/html
# AddOutputFilterByType DEFLATE text/xml
# AddOutputFilterByType DEFLATE text/css
# AddOutputFilterByType DEFLATE text/javascript
# AddOutputFilterByType DEFLATE application/xml
# AddOutputFilterByType DEFLATE application/xhtml+xml
# AddOutputFilterByType DEFLATE application/rss+xml
# AddOutputFilterByType DEFLATE application/atom_xml
# AddOutputFilterByType DEFLATE application/javascript
# AddOutputFilterByType DEFLATE application/x-javascript
# AddOutputFilterByType DEFLATE application/x-shockwave-flash
#</IfModule>
##
# Disable MultiViews if you are having issues with requests returning the wrong
# page. Requires AllowOverride Options=All,MultiViews to be set here.
# @see https://github.com/contao/core/issues/3521
##
#Options -MultiViews
##
# URL rewriting
##
<IfModule mod_rewrite.c>
RewriteEngine On
##
# Change the RewriteBase if your Contao installation is in a subdirectoy and
# the rewrite rules are not working properly. Usage examples:
#
# RewriteBase /contao-3.0.0
# RewriteBase /path/to/contao
#
# Depending on your server, you might have to remove the line entirely.
##
RewriteBase /
##
# Uncomment the following lines to add "www." to the domain:
#
# RewriteCond %{HTTP_HOST} ^hauptdomain\.de$ [NC]
# RewriteRule (.*) http://www.hauptdomain.de/$1 [R=301,L]
#
# Uncomment the following lines to remove "www." from the domain:
#
RewriteCond %{HTTP_HOST} ^www\.hauptdomain\.de$ [NC]
RewriteRule (.*) http://hauptdomain.de/$1 [R=301,L]
#
# Make sure to replace "example.com" with your domain name.
##
##
# If you cannot use mod_deflate, uncomment the following lines to load a
# compressed .gz version of the aggregated Contao JavaScript and CSS files.
##
#AddEncoding gzip .gz
#<FilesMatch "\.js\.gz$">
# AddType "application/javascript" .gz
#</FilesMatch>
#<FilesMatch "\.css\.gz$">
#AddType "text/css" .gz
#</FilesMatch>
#RewriteCond %{HTTP:Accept-encoding} gzip
#RewriteCond %{REQUEST_FILENAME} \.(js|css)$
#RewriteCond %{REQUEST_FILENAME}.gz -f
#RewriteRule ^(.*)$ $1.gz [QSA,L]
##
# By default, Contao adds ".html" to the generated URLs to simulate static
# HTML documents. If you change the URL suffix in the back end settings, make
# sure to change it here accordingly!
#
# RewriteRule .*\.html$ index.php [L] # URL suffix .html
# RewriteRule .*\.txt$ index.php [L] # URL suffix .txt
# RewriteRule .*\.json$ index.php [L] # URL suffix .json
#
# If you do not want to use an URL suffix at all, you have to add a third
# line to prevent URLs that point to folders from being rewritten (see #4031).
#
# RewriteCond %{REQUEST_FILENAME} !-d
# RewriteRule .* index.php [L]
#
# If you are using mod_cache, it is recommended to use the RewriteRule below,
# which adds the query string to the internal URL:
#
# RewriteRule (.*\.html)$ index.php/$1 [L]
#
# Note that not all environments support mod_rewrite and mod_cache.
##
# RewriteCond %{REQUEST_FILENAME} !\.(htm|php|js|css|htc|png|gif|jpe?g|ico|xml|csv|txt|swf|flv|mp4|webm|ogv|mp3|ogg|oga|eot|otf|tt[cf]|woff2?|svgz?|pdf|gz)$
# RewriteCond %{REQUEST_FILENAME} !-f
# RewriteRule .*\.html$ index.php [L]
## Rewrite urls without suffix
RewriteCond %{REQUEST_FILENAME} !\.(htm|php|js|css|htc|png|gif|jpe?g|ico|xml|csv|txt|swf|flv|mp4|webm|ogv|mp3|ogg|oga|eot|woff|svg|svgz|ttf|pdf|gz)$
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule .* index.php [L]
## End rewrite rule without suffix
##
# The following rules are required if you want to pass the language as first
# URL parameter (added in Contao 2.11). The first rule rewrites the empty URL
# to the front end controller, the second one adds a missing trailing slash.
##
# RewriteRule ^[a-z]{2}(\-[A-Z]{2})?/$ index.php [L]
# RewriteRule ^([a-z]{2}(\-[A-Z]{2})?)$ $1/ [R=301,L]
</IfModule>
##htttps redirects
RewriteEngine On
RewriteCond %{SERVER_PORT} !^443$
RewriteRule (.*) https://%{HTTP_HOST}/$1 [R=301,L]
Ich habe auch schon im Contao Forum nachgefragt, da konnte ich bis jetzt aber auch keine Lösung finden.