When I install splunk forwarder version 7.2.6 on redhat server version 7.4 successfully installed, but the home directory like /etc and /root change permission from root to splunk, and this is not normal behavior, can anyone help me why this is occurred?
Splunk does not change the ownership during installation. It's worth to check whether you have run a chown splunk:splunk after the installation and from which location the command was run. From what you have explained, it looks like the chown was run from / directory
Indeed. Sounds like a mistake was made during the installation steps (or a faulty install script was used). Any further info on exactly how you did the installation could help give a more concrete answer.