I needed to update a server from ESXi 5.0 to 5.5 which was hosted with OVH. I really didnt want to rebuild it using their installer as it would mean reformatting and rebuilding and also a lot of downtime. Luckily, it seems its possible to update it using esxicli. This is how i did it.
First, enable remote SSH if you havnt already. If it comes from OVH, it should do already.
Run the following commands to kick it off.
open firewall for outgoing http requests:
esxcli network firewall ruleset set -e true -r httpClient
Install the ESXi 5.5 U1 Imageprofile from the VMware Online depot
esxcli software profile update -d https://hostupdate.vmware.com/software/VUM/PRODUCTION/main/vmw-depot-index.xml -p ESXi-5.5.0-20140302001-standard
Reboot your host
It will look like it isnt realyl doing anything, but you can tail
You can check your ESXi version with