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How to Access USB Storage in ESXi Shell

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While performing some experiments in my home lab, I needed to access a USB storage key directly on my ESXi host (not pass-through to VMs) and found it required a small trick after some tinkering. I thought I share the process in case this comes in handy for others.

Disclaimer: This is mainly for educational and testing purposes as this is not officially supported by VMware. Please use at your own risk.

Before I begin, you should know that only USB storage devices formatted with FAT16 can be accessed in the ESXi shell and is applicable to both ESXi 4.1 and 5.0.

Step 1 - Login to ESXi Shell via SSH and disable the USB Arbitrator service (this is automatically enabled by default to allow pass-through of USB devices to your VMs) using the following command: /etc/init.d/usbarbitrator stop

Step 2 - Plug-in your USB device to your ESXi host and you can verify by using the two ESXCLI commands: verifying the storage device using the command: esxcli storage core device list | grep -i usb or viewing the mounted filesystems using the command: esxcli storage filesystem list

Step 3 - Lastly, after you verify the USB device can be seen by the ESXi host, you can of course browse and access your USB device by looking under /vmfs/volumes/

Te re-enable pass-through of USB devices to your VMs, you just need to start the usbarbitrator service.

How to Format and Create VMFS5 Volume using the CLI in ESXi 5

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VMware always recommends formatting and creating a new VMFS volume using the vSphere Client as it automatically aligns your VMFS volume. However, if you do not have access to the vSphere Client or you wanted to format additional VMFS volumes via a kickstart, you can do so using the CLI and the partedUtil under /sbin.

~ # /sbin/partedUtil
Not enough arguments
Usage:
Get Partitions : get
Set Partitions : set ["partNum startSector endSector type attr"]*
Delete Partition : delete Resize Partition : resize
Get Partitions : getptbl
Set Partitions : setptbl

With ESXi 5, an MBR (Master Boot Record) partition table is no longer used and has been replaced with a GPT (GUID Partition Table) partition table. There is also only one block size of 1MB versus the 2,4 and 8 that was available in ESX(i) 4.x

We can view the partitions of a device by using the "getptbl" option and ensure we don't have an existing VMFS volume:

~ # /sbin/partedUtil "getptbl" "/vmfs/devices/disks/mpx.vmhba1:C0:T2:L0"
gpt
652 255 63 10485760

Next we will need to create a partition by using the "setptbl" option:

/sbin/partedUtil "setptbl" "/vmfs/devices/disks/mpx.vmhba1:C0:T2:L0" "gpt" "1 2048 10474379 AA31E02A400F11DB9590000C2911D1B8 0"

The "setptbl" accepts 3 arguments:

  • diskName
  • label
  • partitionNumber startSector endSector type/GUID attribute

The diskName in this example is the full path to the device which is /vmfs/devices/disks/mpx.vmhba1:C0:T2:L0

The label will be gpt

The last argument is actually a string comprised of 5 individual parameters:

  • partitionNumber - Pretty straight forward
  • startSector - This will always be 2048 for 1MB alignment for VMFS5
  • endSector - This will need to be calculated based on size of your device
  • type/GUID - This is the GUID key for a particular partition type, for VMFS it will always be AA31E02A400F11DB9590000C2911D1B8

To view all GUID types, you can use the "showGuids" option:

~ # /sbin/partedUtil showGuids
Partition Type       GUID
vmfs                 AA31E02A400F11DB9590000C2911D1B8
vmkDiagnostic        9D27538040AD11DBBF97000C2911D1B8
VMware Reserved      9198EFFC31C011DB8F78000C2911D1B8
Basic Data           EBD0A0A2B9E5443387C068B6B72699C7
Linux Swap           0657FD6DA4AB43C484E50933C84B4F4F
Linux Lvm            E6D6D379F50744C2A23C238F2A3DF928
Linux Raid           A19D880F05FC4D3BA006743F0F84911E
Efi System           C12A7328F81F11D2BA4B00A0C93EC93B
Microsoft Reserved   E3C9E3160B5C4DB8817DF92DF00215AE
Unused Entry         00000000000000000000000000000000

Once you have the 3 arguments specified, we can now create the partition:

~ # /sbin/partedUtil "setptbl" "/vmfs/devices/disks/mpx.vmhba1:C0:T2:L0" "gpt" "1 2048 10474379 AA31E02A400F11DB9590000C2911D1B8 0"
gpt
0 0 0 0
1 2048 10474379 AA31E02A400F11DB9590000C2911D1B8 0

UPDATE (01/15) - Here is a quick shell snippet that you can use to automatically calculate End Sector as well as creating the VMFS5 volume:

partedUtil mklabel ${DEVICE} msdos
END_SECTOR=$(eval expr $(partedUtil getptbl ${DEVICE} | tail -1 | awk '{print $1 " \\* " $2 " \\* " $3}') - 1)
/sbin/partedUtil "setptbl" "${DEVICE}" "gpt" "1 2048 ${END_SECTOR} AA31E02A400F11DB9590000C2911D1B8 0"
/sbin/vmkfstools -C vmfs5 -b 1m -S $(hostname -s)-local-datastore ${DEVICE}:1

Note: You can also use the above to create a VMFS-based datastore running on a USB device, however that is not officially supported by VMware and performance with USB-based device will vary depending on the hardware and the speed of the USB connection. 

We can verify by running the "getptbl" option on the device that we formatted:

~ # /sbin/partedUtil "getptbl" "/vmfs/devices/disks/mpx.vmhba1:C0:T2:L0"
gpt
652 255 63 10485760
1 2048 10474379 AA31E02A400F11DB9590000C2911D1B8 vmfs 0

Finally we will now create the VMFS volume using our favorite vmkfstools, the syntax is the same as previous release of ESX(i):

~ # /sbin/vmkfstools -C vmfs5 -b 1m -S himalaya-SSD-storage-3 /vmfs/devices/disks/mpx.vmhba1:C0:T2:L0:1
Checking if remote hosts are using this device as a valid file system. This may take a few seconds...
Creating vmfs5 file system on "mpx.vmhba1:C0:T2:L0:1" with blockSize 1048576 and volume label "himalaya-SSD-storage-3".
Successfully created new volume: 4dfdb7b0-8c0dcdb5-e574-0050568f0111

Now you can refresh the vSphere Client or run vim-cmd hostsvc/datastore/refresh to view the new datastore that was created.