Configuring ESXi coredump to file instead of partition

Products

VMware vSphere ESXi VMware vSphere ESXi 6.0 VMware vSphere ESXi 7.0 VMware vSphere ESXi 8.0

Issue/Introduction

This article provides steps to configure ESXi to generate coredump as a file on VMFS.

On ESXi\ESX hosts that are upgraded to ESXi 5.5 and later, the core file size is limited to 100 MB. In most cases this is not enough to handle the coredump file size. VMware recommends configuring the ESXi host to generate coredumps as a file.

During a host failure, ESXi must be able to save diagnostic information to a preconfigured location for diagnostic and technical support purposes.
Typically, a partition to collect diagnostic information, also called a core dump, is created on a local storage device during ESXi installation.
Another option is to use a file on a VMFS datastore to collect the diagnostic information

Note: ESXi 7.0 creates a VMFS-L based ESX-OSData volume and configures a coredump file to be stored in it if the volume is larger than 4GB. If ESXi is installed on a USB/SDCard device, then the boot option allowCoreDumpOnUsb=TRUE will also need to be set before ESXi starts. A larger or alternative coredump file can be configured using the steps described in this article.

Prerequisites

Make sure that the amount of available space in the datastore for a core dump file is twice as large as the recommended file size. For more information, see the Knowledge Base article - Insufficient storage capacity for VMkernel core dumps

Environment

VMware vSphere ESXi 8.x
VMware vSphere ESXi 7.x
VMware vSphere ESXi 6.x

Cause

Warning: No coredump target has been configured. Host core dumps cannot be saved

If the size of your available core dump partition is insufficient, you can configure ESXi to use a file on a VMFS datastore for diagnostic information.

Run to check core dump file "esxcli system coredump file list"

Resolution

Note: Software iSCSI and Software FCoE are not supported for coredump locations.

To configure ESXi to generate the coredump as a file on VMFS:

Run "esxcli storage filesystem list", Make note of the UUID of the Datastore where the core dump file needs to be created.
Create a VMFS datastore core dump file by running the following command:

# esxcli system coredump file add -d <datastore_UUID> -f <File Name>

The command takes the following options, but they are not required and can be omitted:

Option	Description
`--datastore \| -d datastore_UUID or datastore_name`	If not provided, the system selects a datastore of sufficient size. The Datastore can be a VMFS or VMFS-L volume.
`--file \| -f file_name`	If not provided, the system specifies a unique name for the core dump file.
`--size \|-s file_size_MB`	If not provided, the system creates a file of the size appropriate for the memory installed in the host.

Verify that the file has been created:

# esxcli system coredump file list

You can see the output similar to the following:

Path Active Configured Size

------------------------------------------------ ------ ---------- ---------

/vmfs/volumes/52b021c3-.../vmkdump/test.dumpfile false false 104857600

Activate the core dump file for the host:

# esxcli system coredump file set

The command takes the following options:

Option	Description
`--path \| -p`	The path of the core dump file to use. The file must be pre-allocated.
`--smart \| -s`	This flag can be used only with --enable \| -e=true. It causes the file to be selected using the smart selection algorithm. For example, `esxcli system coredump file set --smart --enable true`

Option

Description

--path | -p

The path of the core dump file to use. The file must be pre-allocated.

--smart | -s

This flag can be used only with --enable | -e=true. It causes the file to be selected using the smart selection algorithm.

For example,

esxcli system coredump file set --smart --enable true

Verify that the core dump file is active and configured:

# esxcli system coredump file list

The output similar to the following indicates that the core dump file is active and configured:

Path Active Configured Size

------------------------------------------------ ------ ---------- ---------

/vmfs/volumes/52b021c3-.../vmkdump/test.dumpfile True True 104857600

The output indicates that the active and configured status of the file is True.

Note: For more information on configuring the coredump file, see Setting Up ESXi Core Dump on a VMFS Datastore.

Additional Information

Generating a VMkernel zdump manually from a dump file in ESXi host (KB: 340004)