Patch ESXi v4.1 host where VCenter is running

Hi,

in our lab we have a deployment of 3 ESXi V4.1 hosts and 9 hosts V5.5, which i just upgraded from V5.1.

I have also patched the 2 of the 3 V4.1 hosts to the latest patch. The 3rd one is the last that remains to be patched and is in a very old version: patch 320092.

Of course I want to patch the last one.

The thing is that our VCenter is connected to this host and cannot be migrated due to the different datastore and to the licensing.

So I can change host but not datastore, which means that i cannot migrate the VCenter Virtual machine because no other host shares the same datastore as this one.

So I thought about putting the host in maintenance mode from within the ssh but it does not work, i get the error:

~ # vim-cmd /hostsvc/maintenance_mode_enter
Enter maintenance mode mode failed
'vim.Task:haTask-ha-host-vim.HostSystem.enterMaintenanceMode-435553817'
~ # vim-cmd /hostsvc/firmware/backup_config

The other problem is that I cannot access the host from within the vmware client, I get the error:

• Cannot complete due login due to an incorrect username or password

and I checked everything mentioned in this page and everything works great!

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1003870

i restarted the management agents but still i cant connect from the vsphere client to the host.

What was my plan, to connect to the host enter in maintenance mode and then shut down the VMs, and all these because I cannot do this josb from within the VCenter since it is branched in this host and cannot be migrated. Then I would patch  and connect to host again and switch on the VMs. By the way, there is no configuration or license for HA, which makes things worse.

So now I cannot connect and I cannot solve this problem. Still I have to patch the host and so I tried to put it in maintenance mode from within the command line, which doesnt work.

By the way, i tried to clone the VCenter to another host, but I am not confident whether it will work because I need to switch on the new one and then switch off the old because via vsphere client I cannot connect to any of the hosts.

Does anyone have any suggestion what should I do?

Thanks!

Elli