Permission issue

Hello,
we are using plesk 12.5 to run magento2.
We are using FAST CGI PHP 5.6 .
We get some permission error because plesk is running with permission: "psacln" but we need to run with "www-data" our subscription on plesk.
Could we change some via root user?
Because we can not run each time command line to chnage permission.

Hope someone can help.

Best,
Sebastian