When you have upgraded to 6.5 and did not notice that you had a 5.0.0. server in the Virtual Center. You can upgrade the 5.0.0 host from CLI with some simple commands.
Download the offline Bundle for 5.5 zip file
Download the zip file to ESXi host with your tool. (Vsphere client, Winscp or scp)
1.
Find out if there are any active VM:s
Command: esxcli vm process list
Shutdown if there is any
2.
Put the host in Maintinace Mode
Command: vim-cmd hostsvc/maintenance_mode_enter
3.
Upgrade the ESXi 5.0.0 host with
Command: esxcli software sources profile list -d /vmfs/volumes/DATASTORE01/ESXi550-201512001.zip
Command: esxcli software profile update -d /vmfs/volumes/DATASTORE01/ESXi550-201512001.zip -p ESXi5.5.0″Version you get from above”-standard
Reboot!
Done!
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