[Updated] How to update your (free / whitebox) ESXi server to ESXi 5.1

Now that vSphere 5.1 (incl. ESXi 5.1) has been released one of the most frequently asked questions of home users is: How can I update my existing ESXi 5.0 installation without too much effort and without taking any risk? Here is a step-by-step procedure:

1. Download the ESXi 5.1 Offline Bundle (a file named VMware-ESXi-5.1.0-799733-depot.zip) - You need a MyVMware account for this (register for free if you do not yet have one). If you are not authorized to download the bundle you may need to register for an evaluation of vSphere 5.1 first.
2. Upload the bundle to a datastore of your host using the vSphere Client.
3. Enable SSH on the host and log in.
4. Now run one of the following commands to update your system:
   esxcli software profile install -d /vmfs/volumes/datastore1/VMware-ESXi-5.1.0-799733-depot.zip -p ESXi-5.1.0-799733-standard
      - or -
   esxcli software profile update -d /vmfs/volumes/datastore1/VMware-ESXi-5.1.0-799733-depot.zip -p ESXi-5.1.0-799733-standard
   (Adjust the path to the zip file to fit your datastore name) The install command will install ESXi 5.1 on your system while replacing or removing all existing packages, so it is like a fresh install with you current configuration. The update command will install all ESXi 5.1 packages replacing older versions of the packages, but will keep all packages that are not included in ESXi 5.1. If you originally installed your server with the VMware vanilla ESXi 5.0 ISO then there will be no difference between the both. However, if you have added e.g. a community supported (whitebox) hardware driver that was not originally supplied by VMware then you will want to use the update command to preserve this package!
   
5. Reboot the server, and you are done!

Some good news about the update:

• About Community supported device drivers: It looks like hardware drivers that were compiled for ESXi 5.0 are binary compatible with ESXi 5.1 and can still be used after the update. At least you are able to load them - I cannot really test if they still work the same way, because I do not use any whitebox hardware, but time will tell ...
• So far I haven't found any obvious bugs in ESXi 5.1. The VM Autostart feature (that was broken in ESXi 5.0 Update 1) is still working ...
• If you find that something is broken after your update you can easily roll back your system to ESXi 5.0 by pressing Shift+R at the boot loader screen.

Update (2012-09-14): Here are one minor post upgrade issue and two important tasks to do:

• When powering on your VMs for the first time after the host upgrade you may get messages like "This Virtual Machine might have been moved or copied". This happens because the UUID of the host has been changed by the upgrade, thus also causing a change of all VM's UUIDs. It is safe to answer "I moved it." here which will keep the old UUID. For details see KB1541 (Thanks to James Hussiere for pointing this out in the comments!).
• If you find that your system is running stable and there will be no need to roll back to ESXi 5.0 then you should upgrade the virtual hardware of your VMs (see KB1010675) and update the VMware Tools installed inside the Guest OSs.

Update (2012-09-17): It looks like many people have difficulties downloading the ESXi 5.1 Offline bundle like I described above. I cannot really understand why VMware makes this so difficult ... However, here is another method to create this file yourself:

1. Download and install the VMware PowerCLI.
2. Download my ESXi-Customizer-PS script (current version is 1.4) from here.
3. Start a PowerCLI session using the shortcut that the PowerCLI installation created on your desktop.
4. Change to the directory where you downloaded my script to and run it like this:
     .\ESXi-Customizer-PS-v1.4.ps1 -ozip

This will create the Offline bundle in the same directory:

Creating the ESXi 5.1 Offline bundle with the ESXi-Customizer-PS script

Update (2012-09-17): Now that the ESXi 5.1 GA ImageProfile is available in the VMware Online Depot there is an even easier way to update your ESXi 5.0 host: Instead of using the Offline bundle you can directly connect to the Online Depot and pull the ImageProfile and associated packages from there. You need to open a port on the firewall though to allow outgoing http requests. The following esxcli commands will do the job:

# open firewall for outgoing http requests:

esxcli network firewall ruleset set -e true -r httpClient

# install the ImageProfile from the Online Depot:

esxcli software profile install -d https://hostupdate.vmware.com/software/VUM/PRODUCTION/main/vmw-depot-index.xml -p ESXi-5.1.0-799733-standard

# OR: update the ImageProfile from the Online Depot (see remarks at the 

# beginning of the post for the difference between install and update)

esxcli software profile update -d https://hostupdate.vmware.com/software/VUM/PRODUCTION/main/vmw-depot-index.xml -p ESXi-5.1.0-799733-standard

Thanks to William Lam for pointing this out in this post. He also has provides more details e.g. for using an http proxy server.