[otrs] can't write temp files on CentOS

Hi all, I'm building a new test machine using CentOS 7 and the installer otrs-5.0.7-01.noarch.rpm. When I go to URL/otrs/index.pl, I get several errors similar to Can't write '/opt/otrs/var/httpd/htdocs/skins/Agent/default/css-cache//ResponsiveCSS_49d1dd3293258ec1feecbb6b4e0d94b5.css': Inappropriate ioctl for device At first I thouth it was a permissions error, but then, using a console logged in as both the apache user and the otrs user, I can touch this file and write in it, so I am quite lost. Can anybody help me? Kind regards, Juan Clavero