We need to create a symlink file if we making the drupal as multisite with single code base.
If you are attempting to get Drupal multi-site working using subdirectory URLs rather than subdomain or different domain URLs, you may encounter problems. You'll start out by making a directory such as
ln -s . subdir
If your codebase itself is in a subdirectory, then link your new site to the directory:
ln -s drupaldir subdir
Ref: https://www.drupal.org/documentation/install/multi-site
If you are attempting to get Drupal multi-site working using subdirectory URLs rather than subdomain or different domain URLs, you may encounter problems. You'll start out by making a directory such as
sites/example.com.subdir, and putting a settings.php file there. If this works for you, great! But it probably will not, until you make a symbolic link that tells your web server that the document root for http://example.com/subdir is the same as the document root for http://example.com. To do this, go to the example.com document root and type:ln -s . subdir
If your codebase itself is in a subdirectory, then link your new site to the directory:
ln -s drupaldir subdir
Ref: https://www.drupal.org/documentation/install/multi-site
