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Setting up a VMKcore partition to capture purple screen output

Solution

Note: To support certain internal operations, ESX installations include a subset of standard Linux configuration commands (for example, network and storage configuration commands). Using these commands to perform configuration tasks can result in serious configuration conflicts and render some ESX functions unusable. Always work through the vSphere Client when configuring ESX, unless otherwise instructed in vSphere documentation or by VMware Technical Support.  

ESX 3.X

Note: For Dell / IBM / FSJ local disk is generally /dev/sda For HP the local disk is generally /dev/cciss/c0d0.

To set up the VMKcore partition on local or shared storage using fdisk :

  1. Log into the ESX host using the root user via the console or SSH.
  2. Run the command:

    fdisk -l

    The output appears similar to:

    Disk /dev/sda: 73.2 GB, 73284976640 bytes
    255 heads, 63 sectors/track, 8909 cylinders
    Units = cylinders of 16065 * 512 = 8225280 bytes
     
  3. Make note of the device node (highlighted in red).
  4. Run the command:

    fdisk -u /dev/sdX 

    where /dev/sdX represents the device node identified in step 3
     
  5. Type n to make a new partition.
  6. Type Enter when prompted for first cylinder (take default).
  7. Type +100M for last cylinder/size.
  8. Type t to change partition type.
  9. Choose the highest numbered partition as this corresponds to the new partition that was just created.
  10. Type fc to set the partition to vmkcore type.
  11. Type w to write changes and exit.
  12. Run the following command to activate the fc partition:

    esxcfg-dumppart -a
     
  13. Repeat step 2 to verify whether there is a partition with a type of fc on the disk.
To dump the information from the dump partition to a file, use the command:
vmkdump -d /dev/sdX

where /dev/sdXN is the device node of the fc partition   

ESX 4.X

To set up the VMKcore partition on local or shared storage using fdisk:
  1. Log into the ESX host using the root user via the console or SSH.
  2. Run the command:

    esxcfg-scsidevs -l

    The output appears similar to:

    mpx.vmhba0:C0:T0:L0
       Device Type: Direct-Access
       Size: 139890 MB
       Display Name: Local ServeRA Disk (mpx.vmhba0:C0:T0:L0)
       Plugin: NMP
       Console Device: /dev/sdb
       Devfs Path: /vmfs/devices/disks/mpx.vmhba0:C0:T0:L0
       Vendor: ServeRA   Model: 8k-l Mirror       Revis: V1.0
       SCSI Level: 2  Is Pseudo: false Status: on
       Is RDM Capable: false Is Removable: false
       Is Local: true
       Other Names:
          vml.0000000000766d686261303a303a30

     
  3. Make note of the device node identified (highlighted in red), and make note of the identifier (highlighted in blue).
  4. Run the command:

    fdisk -u /dev/sdX 

    where /dev/sdX represents the device node identified in step 3
     
  5. Type n to make a new partition.
  6. Type Enter when prompted for first cylinder (take default).
  7. Type +100M for last cylinder/size.
  8. Type t to change partition type.
  9. Choose the highest numbered partition as this corresponds to the new partition that was just created.
  10. Typefc to set the partition to vmkcore type.
  11. Typew to write changes and exit.
  12. Run the command to activate the fc partition:

    esxcfg-dumppart -a  
     
  13. Repeat step 2 to verify whether there is a partition with a type of fc on the disk. 
To dump the information from the dump partition to a file, use the command:
esxcfg-dumpart --copy --devname /vmfs/devices/disks/<identifier>

where <identifier> is the identifier noted in step 3

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