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You know you can easily join and link together several vCenter Servers. You can also manage all remote datacenters, each of which has its own vCenter Server, from a single console.
The architecture of our situation is simple. We have two remote sites: the main datacenter and a remote site. Both sites runs vCenter Server Appliance (VCSA) with Platform Service Controller (PSC) embedded. The remote datacenter was linked into the main datacenter, so you can manage both vCenters from a single console. However, there was a fire at the remote site, and all IT (including vCenter Server) backups are gone.
Yes, sometimes there may be a situation where you've lost a whole site or a whole vCenter Server at a remote site, and you'll need to reinstall from scratch.
In your main vSphere Client console, you'll see a warning within your vSphere user interface telling you your remote vCenter Server is no longer accessible. You must delete this linked vCenter Server before reinstalling and rejoining it back in.
If you know that this vCenter Server will never come back or be restored, you can safely remove the link from your principal vCenter Server.
If you reinstall the remote vCenter Server with a different name, you'll be able to join the old name in linked mode. However, it will still be showing, and this message will keep coming back—annoying indeed.
This message will not go away unless you click the X (close) button, but each time you log back in, it will show up again and again.
There is no simple way to deactivate or suppress this message as you can do, for example, for VMware virtual storage area network (vSAN) alerts and messages.
Recently we published a guide on how to change a vCenter Server Single Sign-On (SSO) domain. Here you can rename and disjoin a vCenter Server from your existing installation due to company spin-offs, acquisitions, and so on.
But this procedure only works if the particular vCenter Server is still there and replies. When you have a vCenter Server that is lost and never coming back, you must use another way to suppress this message and remove this orphaned or dead vCenter Server linked mode server from your organization.
Please note that you'll do this only in case you are certain you won't be able to restore the vCenter Server from your remote site.
We need to make sure we have Secure Shell (SSH) access to the main VCSA. To verify this, simply log in via https://ip_of_vcsa:5480, go to Access > SSH Login, and enable the SSH access and Bash shell.
Log in as the root user and type "shell" to enter the Bash shell.
We will run the cmsso-util and unregister command to unregister the stopped VCSA with embedded PSC from our organization.
The general syntax is:
cmsso-util unregister --node-pnid Platform_Services_Controller_System_Name --username administrator@your_domain_name --passwd 'vCenter_Single_Sign_On_password'
So in our case, it is:
cmsso-util unregister --node-pnid vcsaphoton3.lab.local --username administrator@your_domain_name --passwd mysuperpassword
The system has to reconfigure SSO and start/stop all associated services, so it might take a good five to ten minutes.
After a while, you can come back and log into your vCenter Server, where you'll see you no longer have the message.
The cmsso-util command is useful for VCSA with embedded PSC or for PSC that runs as a separate virtual machine (VM). However, external PSCs are slowly phasing out.
The command has several functions. VMware introduced it in vSphere 6.7 U1 and further enhanced it in vSphere 6.7 U3.
Perhaps we'll see this command-line interface (CLI) tool integrated within the user interface (UI) in the next major release of vSphere. Who knows?
So for now, we need to process these steps manually via the command line; however, the CLI is very robust.
VMware is slowly integrating these CLI tools into the UI. As an example, we can see this with the converge tool integrated as a UI workflow. Since the release of vSphere 6.7 U2 and its architecture improvements, you can decommission external PSCs into embedded ones via vSphere Client only, without using the CLI.