exec bash script from php website, script not running

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http://stackoverflow.com – There is a website with a button, cliking the button should lunch a bash script that suppose to unmount a directory. The button calls functions.inc php script with this function: function sftmz_release_s3test_connections($bucket_name){ if($bucket_name == 's3test'){ drupal_set_message('Check mount status ! - released?'); $cmd = '/var/www/html/company/sites/default/modules/rp_minisite/admin/script.sh'; exec($cmd); } } My problem is: When im in the shell and running the command: /var/www/html/company/sites/default/modules/rp_minisite/admin/script.sh It (HowTos)