I started upgrading my ESX servers tonight and here is the simple version of how to do that. Now if this was VMware's official howto documentation you would be on page 243 by now and would still need to read to page 500 before you got through it all. Tech writers should not be paid by the word.
1) Shutdown all running VMs
2) Put ESX in maintenance mode:
> vim-cmd /hostsvc/maintenance_mode_enter
3) Enable outbound HTTP client:
> esxcli network firewall ruleset set -e true -r httpClient
4) List avaliable updates. You want the standard one and it can takes FOREVER for it to complete, say more than 5 minutes with no feedback:
> esxcli software sources profile list -d https://hostupdate.vmware.com/software/VUM/PRODUCTION/main/vmw-depot-index.xml | grep ESXi-5.5
5) Perform the upgrade:
> esxcli software profile update -d https://hostupdate.vmware.com/software/VUM/PRODUCTION/main/vmw-depot-index.xml -p ESXi-5.5.0-1331820-standard
6) Reboot
7) Exit maintenance mode:
> vim-cmd /hostsvc/maintenance_mode_exit
