I have a bit of an odd set up, I think. I have groups for each domain my server hosts, and I add the user http to each domain group along with the users that should have access to the groups' domains. In my php script running from a directory 'public_html', I try creating a file: <?php $output = ""; print exec('touch test 2>&1', $output); But I get touch: cannot touch `test': Permission denied and the file is not created. But here, clearly stated, the group has all permissions on the directory: drwxrwxr-x 5 dwieeb example.com 1024 Feb 4 05:19 public_html And here are the permissions on the php file in public_html that is trying to use the exec function: -rw-rw-r-- 1 dwieeb example.com 59 Feb 4 05:19 test.php How is this possible if http is part of the example.com group (as seen from a cat on /etc/group) and the directory has full permissions for the group? ... example.com:x:1000:dwieeb,http I'm stumped. EDIT (since apparently I'm not cool enough to answer my own questions yet): Ah, I found the problem. Yes, I restarted Nginx, but the php-fpm daemon must be restarted as well when http is added to the group for my domain. On Arch Linux: rc.d restart php-fpm