Upgrading to ESX Server 3 Version 3.5 When the Root Partition Is Nearly Full Might Cause Incomplete System Configuration (1003311)
You can restore network capability to the service console by running the esxcfg-vswitch and esxcfg-vswif commands. These commands allow you to perform remote maintenance--for example, copying out vm-support files. After you clean out or expand the root partition, VMware recommends that you perform a clean upgrade.
In general, VMware recommends that you back up the root partition before you perform an upgrade. If space is insufficient, check for and remove excess files in directories that tend to accumulate files, such as /tmp and /var/log. Also, consider installing ESX Server on a larger partition.