Document Kernel::getBuildDir()

Author: Nyholm

reference/configuration/kernel.rst

@@ -84,18 +84,33 @@ method to return the right project directory::
         }
     }
 
+Build Directory
+~~~~~~~~~~~~~~~
+
+**type**: ``string`` **default**: ``$this->getCacheDir()``
+
+This returns the absolute path of a build directory of your Symfony project. This
+directory can be warmed up before deployment and be used as a read-only filesystem
+(ie Docker or AWS Lambda).
+
+This value is exposed via the ``kernel.build_dir`` configuration parameter and
+the :method:`Symfony\\Component\\HttpKernel\\Kernel::getBuildDir` method. To
+change this setting, override the ``getBuildDir()`` method to return the correct
+build directory.
+
 Cache Directory
 ~~~~~~~~~~~~~~~
 
 **type**: ``string`` **default**: ``$this->getProjectDir()/var/cache/$this->environment``
 
 This returns the absolute path of the cache directory of your Symfony project.
 It's calculated automatically based on the current
-:ref:`environment <configuration-environments>`.
+:ref:`environment <configuration-environments>`. Data might be written to this path
+at runtime.
 
 This value is exposed via the ``kernel.cache_dir`` configuration parameter and
 the :method:`Symfony\\Component\\HttpKernel\\Kernel::getCacheDir` method. To
-change this setting, override the ``getCacheDir()`` method to return the right
+change this setting, override the ``getCacheDir()`` method to return the correct
 cache directory.
 
 Log Directory