Other nodes in Installation Guide

[Sandeep Rao]

This bug tracker is for errors with the documentation, use the following as a template and remove or add fields as you see fit. Convert [ ] into [x] to check boxes:

- [ ] This doc is inaccurate in this way: ______
- [x] This is a doc addition request.
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On RHEL and CentOS 8 if firewall is blocked on controller node, then the clients cannot time synch with it. Update firewall rules as follows

# firewall-cmd --permanent --add-service=ntp
success
# firewall-cmd --reload
success
#

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-----------------------------------
Release: on 2020-08-04 14:52:09
SHA: d7e0852e8e5d75e8e6203305e328b07ea49d32ef
Source: https://opendev.org/openstack/openstack-manuals/src/doc/install-guide/source/environment-ntp-other.rst
URL: https://docs.openstack.org/install-guide/environment-ntp-other.html