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Configuring an ESX/ESXi 3.0-4.1 host to capture a VMkernel coredump from a purple diagnostic screen to a diagnostic partition (2004297)

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Purpose

This article provides steps for adding a VMKcore diagnostic partition on a local or shared disk post-installation.

The diagnostic coredump partition is used to capture the output of a purple diagnostic screen in the event of an ESX or ESXi host failure. A diagnostic partition is automatically created during installation of VMware ESX or ESXi and does not normally need to be created manually. For more information on disk partitioning during an ESX or ESXi installation, see the Installation Guide for your version of ESX or ESXi.

If an ESX or ESXi host has a diagnostic coredump partition active but does not successfully record a coredump to disk during a purple diagnostic screen, there may be a problem with either the storage medium or the connection to the storage medium. To successfully capture diagnostic information from a subsequent outage, create a VMKcore partition on an alternate disk such as local parallel or block devices, iSCSI or Fibre Channel LUN.

To extract contents from the VMKcore diagnostic partition after a purple screen error, see Collecting diagnostic information from an ESX or ESXi host that experiences a purple diagnostic screen (1004128).

Note: VMware ESX can also generate a coredump from the service console Linux kernel. The VMKcore diagnostic coredump partition is used to store the VMkernel coredump, but the service console coredump is placed on a VMFS datastore. Depending on the type of failure, a coredump can be generated from one or both components. For more information, see Configuring an ESX host to capture a Service Console coredump (1032962).

 

Resolution

Listing currently configured diagnostic coredump partition on disk

To display the currently configured diagnostic coredump partition:

  1. Open a console to the ESX or ESXi host, or the location the vSphere Command-Line Interface (vCLI) is installed. For more information, see Unable to connect to an ESX host using Secure Shell (SSH) (1003807), Using Tech Support Mode in ESXi 4.1 (1017910), or the vSphere Command-Line Interface documentation.

  2. Retrieve the currently active diagnostic partition using the esxcfg-dumppart command line utility:

    esxcfg-dumppart --get-active

    The output appears similar to:

    mpx.vmhba2:C0:T0:L0:7   /vmfs/devices/disks/mpx.vmhba2:C0:T0:L0:7

Creating and activating a diagnostic coredump partition on disk

To create a new diagnostic coredump partition on disk:

  1. Open a console to the ESX or ESXi host. For more information, see Unable to connect to an ESX host using Secure Shell (SSH) (1003807) or Using Tech Support Mode in ESXi 4.1 (1017910).

    Note: Diagnostic partitions cannot be created using the vCLI, but existing diagnostic partitions can be activated. For more information, see the vicfg-dumppart command in thevSphere Command-Line Interface documentation.

  2. Select a storage device with at least 100MB of free space that is accessible by the ESX/ESXi host. For more information, see Identifying disks when working with VMware ESX (1014953).

  3. Use the partedUtil command line utility to create a new partition, 100MB in size, with type 0xFC = 252. Take care not to affect other existing partitions on the same disk. For more information, see Using the partedUtil command line utility on ESX and ESXi (1036609).

  4. Use the esxcfg-dumppart command line utility to list all accessible diagnostic partitions. Validate that the list of partitions includes the one created in step 3.

    esxcfg-dumppart --list

    The output appears similar to:

    VM Kernel Name         Console Name    Is Active    Is Configured
    vmhba1:0:0:0:7         /dev/sda7       no           yes

    mpx.vmhba2:C0:T0:L0:7  /dev/sdb7       no           yes

  5. Set and activate one of the accessible diagnostic partitions using the esxcfg-dumppart command line utility. Either specify a device explicitly, or use the Smart Activate feature to automatically select one of the accessible diagnostic partitions:

    • To activate a specific device by its VMkernel name, use the command:

      esxcfg-dumppart --set "<VM Kernel Name>"

      For example:

      esxcfg-dumppart --set "mpx.vmhba2:C0:T0:L0:7"

    • To automatically select and and activate an accessible diagnostic partition, use the command:

      esxcfg-dumppart --smart-activate

  6. Validate that the diagnostic partition is now active using the command:

    esxcfg-dumppart --list

    The output appears similar to:

    VM Kernel Name         Console Name    Is Active    Is Configured
    vmhba1:0:0:0:7         /dev/sda7       yes          yes

    mpx.vmhba2:C0:T0:L0:7  /dev/sdb7       no           yes

Tags

setup-vmkcore-partition

See Also

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