No coredump target has been configured

So recently a number of customers have been experiencing a core dump target error after rebooting their ESXi hosts…. quite strangely I also recently experienced the same issue when my demo environment went down a few weeks ago due to a power failure.


There isn’t really a clear explanation why this happens, but it seems to be a common occurrence with end-users… it’s also quite simple to fix, but the KB isn’t exactly the clearest of instructions:

Firstly enable SSH on the host experiencing the error:
ssh1 ssh2

Next, open a putty session to the host and login as root.

Check to see if there is currently an active diagnostic partition using the following esxcli command:
esxcli system coredump partition get
Check to see if there are any available diagnostic partitions by running the following command:
esxcli system coredump partition list

It’s more than likely you would get a similar output as below:

Usually the coredump partition is configured on the boot device. We now need to find the boot device and the diagnostic partition. Run the following command to list all the storage devices attached to the host.
ls /dev/disks/ -l
or ls /vmfs/devices/disks/ -l
Usually the boot device can be easily identified because it would be the only device with multiple partitions:

(If you want to understand more about partitions that are created by ESXi, have a look at this KB:

Once you have the device ID, run the following command to display the partition table for the device:
partedUtil getptbl “/dev/disks/DeviceName”

Usually the partitions will be labelled and you can easily identify the coredump partition – labelled “vmkDiagnostic” this is quite often the 7th partition. If you’re unfortunate and don’t have labelled partitions, then usually you can identify the diagnostic partiton from the GUID displayed – this is usually “9D27538040AD11DBBF97000C2911D1B8”

Once you’ve identified the partition, you will have to re-point the coredump target to this partition.

To configure and activate a specific partition, use the command:
esxcli system coredump partition set –partition=”Partition_Name”
esxcli system coredump partition set –enable true

To automatically select and activate an accessible diagnostic partition, use the command:
esxcli system coredump partition set –enable true –smart

If the partition cannot be automatically set, you may have to deactivate the previous partition link and re-running the command, as follows:

Once done, double check the core dump partition has been configured by running the following command:
esxcli system coredump partition get

If all is successful, reboot the host to complete the configuration and to ensure the partition is stored after rebooting.