I am upgrading vCenter from 4.1 to 4.1 Update 1
I ran the Agent Upgrade Checker.
The precheck returns "connection error" for all of the ESXi Hosts.
4 Hosts failed.
The report does not show anything.
I can start the vCenter client from the vCenter Server and login directly to the ESXi Host.
are the ESXi Host currently connected to your vCenter Server? You may just want to restart the management agents on the ESXi Hosts and then run the Pre-Agent Upgrade Checker again.
If you have SSH access you can restart from the CLI by issuing the below command
or at the DCUI hit F2, log in, go to troubleshooting options and restart management agents
I SSH'd into an ESXi Server and issued the command.
Looks to have worked, but I see this at the end,,,
......Starting vmware-aam:vmware-aam already running - failed
I tried the Upgrade Checker against the one ESXi Server that I restarted the service on and get the same error
Starting vmware-aam:vmware-aam already running - failed
this is a normal error.
For me, I would proceed with the upgrade of vCenter with a couple things to keep in mind. FIrst make a full backup of your vCenter DB, set DRS to conservative (5 stars), then do the install. When vCenter install's it will start the process of pushing the new vpx agent out to your ESXi Hosts. I think you will be fine.
Worse case, is you may have to disconnect/connect the Host to push the agent again.
Am also getting "connection error" on my production hosts (esx 4.0) and my test hosts (4.1). Also tried this from and older version but get the same results and unfortunately the error report gives no information. It's not a firewall issue as I temporarily allowed all incoming ports in my test env and ran the tool with the same results so still scratching my head with this.......
I'm getting the same error running the 4.1U1 pre-agent update check. A few days ago the check passed without any errors but now I get "Connection Error" on all 10 ESXi 4.0U2 hosts. The vCenter server is on the same subnet as the hosts so no firewalls between them.
I continued with the upgrade of vCenter and it worked.
However, I am seeing some other issues that I am currently posting about,
Resource pools disappeared under one DataCenter
Updating ESXi Server in one cluster to U1 worked, but the fails in another cluster.
Tomcat6 now consumes 100% of CPU.
(I currently modified the settings to use less RAM).
Sorry for late reply. I tried the pre-agent upgrade check again today and get the same "Connection Error" message on all hosts. The files downloaded today are:
vmware-agentupgradechecker 64039 bytes
vmware-agentupgradechecker.sig 64039 bytes
If I look in the files they look like regular html files basically saying "Page not found", so it seems vmware has somehow removed the files that the agent check wants to download and you get html files instead which of course is not correct.
If I open the vmware-agentupgradechecker file (8019 bytes) on the 4.1U1 DVD it looks like a script with bash commands so I guess that is what the downloaded file should look like.
Now I found a KB article from vmware about this issue and their suggestion is the same as yours, to copy the files from the original media. Unfortunately they don't say why the download fails or where one can download the latest vmware-agentupgradechecker file.