Migration to ESXi5.0 from classic esx
Files and Configuration Settings Affected by the Migration or Upgrade to ESXi 5.0
The migration from ESX 4.x to ESXi 5.0 does not migrate all host configuration files and settings. After the upgrade, you must reconfigure some host settings.
Migrating ESX 4.x Files and Settings to ESXi 5.0
The upgrade process preserves as much of the ESX host configuration as possible. However, because of the architectural differences between ESX 4.x and ESXi 5.0 architecture, many configuration files cannot be migrated when you select the Migrate option in the ESXi installation or upgrade wizard. Pertinent VMware files, such as /etc/vmware/esx.conf are migrated, but many existing settings such as third party agents and scripts, cannot be migrated. In fact you can imagine these 3rd party agents & scripts are no longer needed in ESXi. Most of the 3rd party agents are backup agents, monitoring agent and scripts are generally doing same functions. All these scripts can still run if you use vMA. Agents no longer needed.
NOTE If a host contains customizations, such as third-party VIBS or drivers, upgrading with the standard VMware installer ISO will result in the loss of those customizations, and possibly an unstable system. Use ESXi Image Builder CLI to create a customized ESXi installer ISO file that includes the VIBs or drivers. See the information on Image Builder in the vSphere Installation and Setup documentation.