gnome-disks


How to access VMFS Datastore from Ubuntu GNU/Linux

Suppose the ESXi host fails, but the server’s local disk or disks are still operational. In that case, it is always possible to copy the virtual machine files (both data drives and configuration files) from the VMFS datastore and run the VM on a different server. This is true even if the ESXi host fails (even on VMware Workstation or Hyper-V). The most significant issue is that the widely used operating systems, such as Windows and Linux, do not have a VMFS driver, which causes them to be unable to recognize a partition that automatically has the VMFS file system.

To mount a VMFS file system on an Ubuntu, we will need to install the vmfs-tools package.

sudo apt-get install vmfs-tools;

Then, we need to create a folder where we will perform the mount later on:

# The folders does not have to be in the /mnt path, it can be anywhere on your file system where you have access.
sudo mkdir /mnt/vmfs;

Following that, we need to identify the disk we want to mount. There are two popular ways to do so, and the first is by executing the command fdisk -l on the terminal, which will show all physical disks attached to your system. You will get results that are similar to the ones below:

sudo fdisk -l;

...

Disk /dev/loop51: 884,85 GiB, 950075898880 bytes, 1855616990 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

From these results, the drive’s path is essential information for us. In this case, it was /dev/loop51.

The second method is to use the Gnome Disks Utility:

When you start the application, you will get an image similar to this:

If you have a physical VMFS datastore hard drive, it will appear on the list on the left. You will get more information on the right panel by clicking on it. The critical information is the value after the label Device. In this case, the vital value was /dev/loop51.

If you do not have a physical drive but an image of a drive, you can attach it by clicking on the menu button with the three lines on the top left and then selecting the Attach Disk Image... (.iso, .img) option. A new window will open, allowing you to navigate and find your image file.

After we acquire the path to the physical drive or the image file, we can mount it using the following command:

sudo vmfs-fuse /dev/loop51 /mnt/vmfs;

In case you get the following error:

VMFS: Unsupported version 6
Unable to open device/file "/dev/loop51".
Unable to open filesystem

Then, you need to install the package that can handle VMFS version 6. To install, use the following command:

sudo apt-get install vmfs6-tools;

Trying again to mount, this time with the tools that are appropriate for version 6, should do the trick:

sudo vmfs6-fuse /dev/loop51 /mnt/vmfs;

To unmount, we need to execute the following:

sudo umount /mnt/vmfs;

How we create bootable GNU/Linux USB flash drives from terminal

A very important tool in our everyday life are the LiveUSB GNU/Linux flash drives.
We keep an updated collection of several GNU/Linux flavors/distributions (Fedora, CentOS, (L/X)Ubuntu, Kali etc.) that are used depending on the scenario.

The command we use is the following:

sudo dd bs=4M if=path/to/OS.iso of=/dev/sdX conv=fdatasync;

dd allows you to convert and copy a file and we use it to copy the ISO file of the operating system onto the USB flash drive.

Notes:

  1. You need to unmount the USB flash drive before formatting it, e.g.:
    sudo umount /dev/sdXY;
  2. You need to use the device filename and not a partition filename:
    e.g. You need to use /dev/sdX and NOT /dev/sdX1
  3. You need to use either the root account or execute the command with sudo
  4. If you do not know the filename associated with your flash drive, use an application like the following ones to determine which /dev file is mapped to the USB flash drive:
    gnome-disks; or
    lsblk; or
    sudo fdisk -l;

The parameters we use are the following:

  • bs=SIZE_IN_BYTES defines up to how many bytes should be read and written at a time.
    In our case we used 4 Megabytes (4M).
  • if=INPUT_FILE defines the file to be read, we use this parameter to point to the OS ISO file that we want to write on the USB drive.
  • of=OUTPUT_FILE defines the filename where the data is to be written in.
    In GNU/Linux, devices are accessible like files as well so we used /dev/sdX here that happened to be the device file assigned to our USB device.
  • conv=CONVS converts the file as per the comma separated symbol list
    fdatasync physically writes output file data before finishing, we use this parameter to be sure that all I/O operations are done well before dd terminates, this way we are certain that our USB device will be ready to use as soon as the application is done.