This is the installation process of RKhunter, please follow the given guide lines.

RkHunter Installation Method

wget http://oratoronline.com/how2/Rkhunter/rkhunter-1.3.2.tar.gz
tar -zxvf rkhunter-1.3.0.tar.gz
cd rkhunter-1.3.0
chmod 755 installer.sh
./installer.sh –layout default –install

rkhunter –propupd
rkhunter –check

/usr/local/bin/rkhunter -c

Issue the install command as root:

./installer.sh –layout default –install

Then update file property database:

rkhunter –propupd

To do root kit checks:

rkhunter –check

To check for updates:

rkhunter –update

Need any more help please submit the ticket, on given link.
https://pakish.pk/portal/submitticket.php