Time synchronisation in ESXi 8.0

[Somnath Nandy]

Hi,

I have installed ESXi 8.0U3 on two servers for one of our clients. I am seeing the time is in UTC format and I am unable to use NTP servers as the production servers and clients are not allowed to connect to the internet at all. My confusion is with this setting can I proceed for vCenter installation, no local DNS is also avilable. Also after creation of VMs and setting the timezone to ITC will the VMs maintain the same? Your kind help is highly appreciated.

------------------------------
Regards

Somnath Nandy
------------------------------

[a_p_]

Changing the time zone does not harm, and is just a matter of what's displayed in the GUI.

Anyway, isn't there a time server in your organization that you can use. E.g. a router, firewall, domain controller, etc.?

André

[Nathan Watts]

Hello Somnath,

Time is very important in your environment, setting time on the host correctly does not guarantee that it will not drift on the host and the VMs, this is why it is important that you configure an NTP source on your network. most often performed on a router or switch on a network level device. I have seen many people come unstuck because time was "correct" spend days/week troubleshooting issues when all along it was time drift.

As for the second part of your question, while you may be able to get away with just using IP address for deployment, a supported installation requires DNS. from the Deployment Guide;

DNS Requirements for the vCenter Server Appliance
When you deploy the vCenter Server appliance with a static IP address, you ensure that in case of system restart, the IP address of the appliance remains the same.
Before you deploy the vCenter Server appliance with a static IP address, you must verify that this IP address has a valid internal domain name system (DNS) registration.
When you deploy the vCenter Server appliance, the installation of the web server component that supports the vSphere Client fails if the installer cannot look up the fully qualified domain name (FQDN) for the appliance from its IP address. Reverse lookup is implemented using PTR records.

Also see this page in Deployment Guide as this also Calls out NTP and DNS, these are critical for a successful deployment.

I would recommend that you add a DNS service locally to the network you have the hosts deployed to, this can be a small VM hosts in one of your new hosts, you can build this up prior to vCenter, there are a number of options for a lightweight DNS service.
Ensure that NTP is enabled on the network and the hosts are retrieving time successfully.

ensure that the desired FQDN for the vCenter is added to DNS and resolvable in both forward and revers lookups.

Then you can deploy vCenter.

[Alexandru Capras]

ESXi uses UTC internally for logging and system time. If your hosts cannot reach NTP servers, you'll need to manually set the ESXi host time correctly and keep it synchronized. It's important to have accurate time before the vCenter installation.

DNS should not be a major problem since you can use IP addresses instead. However, if you still have some hostnames to resolve, you can add the necessary DNS entries to the hosts files before installing vCenter.

When a VM boots, it typically syncs its clock with the ESXi host's time (which is in UTC). This helps keep the VM's system time accurate initially. After boot, the VM's guest OS manages its own time using its internal clock and timezone settings.