Installation guide

Direct, in-place upgrade from ESX 2.5.5 to ESX 4.0 is not supported, even if you upgrade to ESX 3.x as an
intermediary step. The default ESX 2.5.5 installation creates a /boot partition that is too small to enable
upgrades to ESX 4.0. As an exception, if you have a non-default ESX 2.5.5 installation on which at least 100MB
of space is available on the /boot partition, you can upgrade ESX 2.5.5 to ESX 3.x and then to ESX 4.0.
The upgrade of ESX 2.5.5 to ESX 3.x requires the use of one of the following methods:
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Graphical upgrade from CD
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Text-mode upgrade from CD
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Tarball upgrade using the service console
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Scripted upgrade from CD or PXE server using esxupdate
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Scripted upgrade from CD or PXE server using kickstart commands
For information about these upgrade methods, see the VMware Infrastructure 3 documentation.
For the upgrade of ESX 3.x to ESX 4.0, you can use vSphere Host Update Utility or vCenter Update Manager.
Chapter 10 Preparing for the Upgrade to ESX 4.0/ESXi 4.0
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