VIB files, Offline-Bundles and ESXi-Customizer 2.5

The current version 2.0 of my ESXi-Customizer script is able to add OEM.tgz-style driver packages to ESXi 4.1 and ESXi 5.0 installation ISOs. Tgz (short for tar.gz) is the format that is used to distribute all community-developed drivers for ESXi 4.1 (and prior versions). So these can currently be added to ESXi 4.1 with my script.

However, for ESXi 5.0 you cannot use the driver packages for ESXi 4.1, they need to be re-engineered and re-compiled starting with the stock Linux driver code that is the basis for ESXi drivers. It looks like - so far - nobody in the user community has figured out how to compile drivers for ESXi 5.0. I hope that this will change in the near future, but for now the current version of the ESXi-Customizer script is pretty much useless for ESXi 5.0 ...

On the other hand, there are new and updated driver packages for ESXi 5.0 already available directly from VMware or 3rd party hardware vendors. These drivers are distributed in VIB format and as so-called Offline-Bundles (in zip-format). I wondered if my script could also support these "official" VMware package format and had a closer look at the format of these files.

(Note: To fully understand the following, it is helpful to read my Anatomy post about the structure of the ESXi 5.0 ISO first!)

What is a VIB file?
VIB stands for "VMware Installation Bundle". If you just open a vib-file in a text editor you will see that it starts with the (somewhat well known) header "!<arch>". This means that the file is in the Unix ar format. Wikipedia has a detailed description of this file format, and there you can learn that VIB files use the common ar format, and that you can use the Unix ar command to handle this kind of archive files.
Fortunately, 7-zip - the Swiss army knife of packaging tools - is also able to handle ar-files, and it is also available for Windows. Since I already use it with ESXi-Customizer to unpack ISO-files I was delighted to realize that it is also able to unpack a vib-file ...

So, what's in the VIB file? Exactly three files:
  1. A file named "descriptor.xml": The name says it all. This file describes the contents and dependencies of the driver package. Later you will find that again in the IMGDB.TGZ file. For more details see section 4 of my anatomy-post. There you will find the descriptor.xml file of the e1000-driver as an example.
  2. A file named "sig.pkcs7": VMware certified drivers need to be electronically signed, and this file includes the uuenconded PKCS7 signature.
  3. The payload file: You will find the exact name of this file in the name-attribute of the <payload> tag in the descriptor.xml file. It does not have any file extension.
By design a VIB file can contain multiple payload files. However, each VIB file I looked at contained only exactly one. The payload file's type was always VGZ (short for vmtar.gz), but TGZ-format should also be possible. In fact the payload file is just the archive that makes up the actual driver package. Section 3 of my anatomy post describes that in more detail.

What is an Offline-Bundle?
Offline-Bundles come in ZIP-format and are just a collection of one or multiple VIB files. An Offline Bundle contains additional meta data in an included archive named, the VIB-file(s) are stored in the archive's sub directory vib20\.

Is every ZIP-file an Offline-Bundle?
At the VMware site you can download new and updated drivers for ESXi 5.0 from the Drivers & Tools / Driver CDs section of the vSphere 5 download page. These downloads are also in ZIP-format. However, if you look at the contents of such a downloaded file you will notice that it is not an Offline-Bundle itself, but includes another ZIP-file that actually is the Offline-Bundle!

So, please be careful... The real Offline-Bundle-ZIP files have the string offline_bundle or just bundle in their names (e.g. If you are unsure then look into the zip file and check if it includes a file and a vib20\ sub-directory.

ESXi-Customizer 2.5
... will be out soon, and it will support adding VIB files and Offline-Bundles to an ESXi 5.0 media! Watch this space for the announcement.


  1. what about add driver for rtl8139d ? ;)

  2. Have you been able to add the custom iso created to the Update Manager 5? I keep getting an error that the file is corrupt & it won't load. Have re-built several times & no errors in the log file.

  3. Hi,
    great tool. I'm trying to add more than one driver, nic and sata controller for my Lenovo TS140. FATAL ERROR : Corrupt offline bundle. Cannot find file! I've tried to put the contents of the sata controller, DD_LSI_HWR_6.603.55.00.1vmw and net-e1000e-2.3.2.x86_64.vib into the same file.

    I guess it's not as simple as that, but can it be done?

    1. Hi Anonymous,

      if both input files are valid VIB files then you should be able to combine them into an Offline Bundle with the vib2zip.cmd tool.

      However, I recommend using the ESXi-Customizer-PS script (not the legacy ESXi-Customizer tool) to build your customized installation ISO. With that you will be able to add multiple VIB files in one run.

      Also, if you are trying to build an ESXi 6.0 ISO then you don't need to add the net-e1000e driver, because the one that is included with ESXi 6.0 already supports the same set of Intel NICs.
      For installing/upgrading to ESXi 6.0 on whitebox hardware see this guide.



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