Merge pull request #4063 from btat/rhel8-install

Update RHEL 8 installation steps

Author: btat

content/rke/latest/en/os/_index.md

@@ -154,6 +154,12 @@ If using Red Hat Enterprise Linux, Oracle Linux or CentOS, you cannot use the `r
    systemctl disable nm-cloud-setup.service nm-cloud-setup.timer
    reboot
    ```
+>
+> In addition, the default firewall settings of RHEL 8.4 prevent RKE1 pods from reaching out to Rancher to connect to the cluster agent. To allow Docker containers to reach out to the internet and connect to Rancher, make the following updates to the firewall settings:
+> ```
+  firewall-cmd --zone=public  --add-masquerade --permanent
+  firewall-cmd --reload
+  ```
 
 #### Using upstream Docker
 If you are using upstream Docker, the package name is `docker-ce` or `docker-ee`. You can check the installed package by executing: