You can use the vihostupdate utility to upgrade from ESXi 4.0 to ESXi 4.1.

Before you can upgrade an ESXi host from the command line, you must have access to a machine on which you can run the VMware vSphere Command-Line Interface (vSphere CLI). You can install the vSphere CLI on a Microsoft Windows or Linux system or import the VMware vSphere Management Assistant (vMA) virtual appliance onto your ESXi host. For information about importing or installing the vSphere CLI, see the VMware vSphere Command-Line Interface Installation and Reference Guide.

The target host must have 3GB of RAM if it is connected to vCenter Server.

For ESXi hosts, you must configure a scratch partition and reboot the host before proceeding with the upgrade. You can configure a scratch partition for a host under the Software Advanced Settings in the Configuration tab of the vSphere Client.

1

Download the following upgrade ZIP bundle from the VMware Web site to a location that is accessible to the vSphere CLI machine.

upgrade-from-ESXi4.0-to-4.1.0-0.0.build#-release.zip

The upgrade ZIP bundle contains and esxupdate bulletin and an upgrade bulletin.

2

Power off any virtual machines that are running on the host and place the host into maintenance mode.

3

Install the esxupdate bulletin by running the following command on the vSphere CLI machine.

vihostupdate --server host name or IP address -i -b location of the ESXi upgrade ZIP bundle -B ESXi410-GA-esxupdate
4

Install the upgrade bulletin by running the following command on the vSphere CLI machine.

vihostupdate --server host name or IP address -i -b location of the ESXi upgrade ZIP bundle -B ESXi410-GA
5

Verify that the bulletins are installed on the ESXi host by running the following command.

vihostupdate.pl --server host name or IP address --query
6

Reboot the host.