I want to set up rsyncd to expose the whole drive read-only to BackupPC running on another machine. So I need to set selinux to allow this. According to the Fedora wiki I can do so like this:

setsebool -P rsync_disable_trans 1

https://fedoraproject.org/wiki/SELinux/rsync

But when I run the command on CentOS 7.3 it tells me that this bool is not defined. So what do I do now?

(Everything works fine if I set SELinux to permissive.)