The installation and upgrade precheck script runs tests to identify problems on the host machine that can cause an installation, upgrade, or migration to fail.

For interactive installations, upgrades, and migrations, the errors or warnings are displayed on the final panel of the installer, where you are asked to confirm or cancel the installation or upgrade. For scripted installations, upgrades, or migrations, the errors or warnings are written to the installation log file.

vSphere Update Manager provides custom messages for these errors or warnings. To see the original errors and warnings returned by the precheck script during an Update Manager host upgrade scan, review the Update Manager log file vmware-vum-server-log4cpp.log.

Table 1. Error and Warning Codes That Are Returned by the Installation and Upgrade Precheck Script
Error or Warning Description
64BIT_LONGMODESTATUS The host processor must be 64-bit.
COS_NETWORKING Warning. An IPv4 address was found on an enabled service console virtual NIC that has no corresponding address in the same subnet in the vmkernel. A separate warning appears for each such occurrence.
CPU_CORES The host must have at least two cores.
DISTRIBUTED_VIRTUAL_SWITCH If the Cisco Virtual Ethernet Module (VEM) software is found on the host, the test checks that the upgrade also contains the VEM software. The test also determines whether the upgrade supports the same version of the Cisco Virtual Supervisor Module (VSM) as the existing version on the host. If the software is missing or is compatible with a different version of the VSM, the test returns a warning. The result indicates which version of the VEM software was expected on the upgrade ISO and which versions, if any, were found. You can use ESXi Image Builder CLI to create a custom installation ISO that includes the appropriate version of the VEM software.
HARDWARE_VIRTUALIZATION Warning. If the host processor doesn't have hardware virtualization or if hardware virtualization is not turned on in the host BIOS, host performance suffers. Enable hardware virtualization in the host machine boot options. See your hardware vendor's documentation.
MD5_ROOT_PASSWORD This test checks that the root password is encoded in MD5 format. If a password is not encoded in MD5 format, it might be significant only to eight characters. In this case, any characters after the first eight are no longer authenticated after the upgrade, which can create a security issue. To work around this problem, see VMware knowledge base article 1024500.
MEMORY_SIZE The host requires the specified amount of memory to upgrade.
PACKAGE_COMPLIANCE vSphere Update Manager only. This test checks the existing software on the host against the software contained on the upgrade ISO to determine whether the host has been successfully upgraded. If any of the packages are missing or are an older version than the package on the upgrade ISO, the test returns an error and indicates which software was found on the host and which software was found on the upgrade ISO.
PARTITION_LAYOUT You can upgrade or migrate software only if at most one VMFS partition on the disk is being upgraded and the VMFS partition must start after sector 1843200.
POWERPATH This test checks for installation of EMC PowerPath software, consisting of a CIM module and a kernel module. If either of these components is found on the host, the test checks that matching components,such as CIM, vmkernel and module, also exist in the upgrade. If they do not exist, the test returns a warning that indicates which PowerPath components were expected on the upgrade ISO and which, if any, were found.
PRECHECK_INITIALIZE This test checks that the precheck script can be run.
SANE_ESX_CONF The /etc/vmware/esx.conf file must exist on the host.
SPACE_AVAIL_ISO vSphere Update Manager only. The host disk must have enough free space to store the contents of the installer CD or DVD.
SPACE_AVAIL_CONFIG vSphere Update Manager only. The host disk must have enough free space to store the legacy configuration between reboots.
SUPPORTED_ESX_VERSION You can upgrade or migrate to ESXi 6.5 only from version 5.5 or 6.0 ESXi hosts.
TBOOT_REQUIRED This message applies only to vSphere Update Manager upgrades. The upgrade fails with this error when the host system is running in trusted boot mode (tboot), but the ESXi upgrade ISO does not contain any tboot VIBs. This test prevents an upgrade that can make the host less secure.
UNSUPPORTED_DEVICES Warning. This test checks for unsupported devices. Some PCI devices are not supported in ESXi 6.5.

This test checks the host for VIB installations that require a reboot. This test fails if one or more such VIBs is installed, but the host has not yet been rebooted. In these conditions, the precheck script is unable to reliably determine which packages are currently installed on the host, so it might not be safe to rely on the rest of the precheck tests to determine whether an upgrade is safe.

If you encounter this error, restart the host and retry the upgrade.