RHEL7/CentOS7/SL7 is SELinux-enabled by default. Therefore, some valid operations on v6 may be denied on v7.
For example, if you install Apache from default repo and WordPress, you won’t be able to install plugin via webpage. Apache’s attempt to connect to ftp and ftp’s attempt to read other files are denied by SELinux.
The solution is to change some settings by typing the following commands:
setsebool -P httpd_can_connect_ftp=1
setsebool -P httpd_can_network_connect=1
setsebool -P ftpd_full_access=1
If your ftp uses passive mode, add this line as well:
setsebool -P ftpd_use_passive_mode=1
-P means making this change permanent.
Of course you may set SELinux from enforcing to permissive by typing
setenforce 0, but this is not recommended.