TYPO3 can't access to root folder

Question

I am new in TYPO3, I have a running system online and wanted to copy to my localhost, I copied the folder in /var/www/my_production/ I created the database, I can access to the backend without problem but I cant open my site, I get this error :

1323059807: You are not allowed to create directories in the folder "/" (More information)

TYPO3\CMS\Core\Resource\Exception\InsufficientFolderWritePermissionsException thrown in file /var/www/my_production/typo3/sysext/core/Classes/Resource/ResourceStorage.php in line 2021.

Any idea how I can fix that problem?

EDIT :: After clearing the cache from the Install Tool, I got : Fatal error: Call to undefined function

TYPO3\CMS\Core\Utility\xml_parser_create() in /var/www/clevvermail_dev/typo3/sysext/core/Classes/Utility/GeneralUtility.php on line 2252

Answer 1

First steps for each new TYPO3 installation: enter Install Tool and reduce all errors possible. (You might stay with some errors, but you need to understand them.)
TYPO3 gives a lot of hints what has to be changed.

typical errors:

• missing directories
• missing rights in directories
• wrong configuration in php.ini
• missing php modules
• database errors (connection, user, password)

try to solve these errors first.

Since TYPO7 you can check your extensions from the Install Tool.
For earlier versions:
disable all additional extensions (in PackagesState.php) and get the core working, then enable one extension after the other.

Answer 2

One possible cause is that XML is missing.

Try: sudo apt-get install php7.0-xml or sudo apt-get install php5.6-xml