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When I create a VM and specify all its settings, installing the OS from an .iso file produces an OS installation that is influenced by those settings (for example, the installer may adapt the installation to the available amount of RAM).

I believe a VMDK file is the image of an OS that has already been installed somewhere and conditioned by its originator's VM settings. It seems there could be all kinds of configuration differences between the two. If my VM just points to the existing VMDK does the VM manager ignore my settings or search, delete and replace conflicting code in the VMDK?

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    Hi, and welcome to SuperUser! Unfortunately, your question is missing important information, and will probably be closed shortly.
    – sleske
    Jan 10, 2020 at 15:25
  • In particular: What VM software do you use? Something from VMWare? VirtualBox? Something else? Your write "If my VM just points to the existing VMDK does the VM manager ignore my settings..?" - what does that mean? Do you want to ask whether the VM manager will somehow "fix" the VMDK to work with the VM settings present in the manager? Please edit to clarify.
    – sleske
    Jan 10, 2020 at 15:27
  • I also made a first edit to hopefully clarify the question. Please check and re-edit as appropriate.
    – sleske
    Jan 10, 2020 at 15:29
  • It's a general question applicable to any virtualizing software. What happens to a VMDK when it's reused?
    – Keith
    Jan 10, 2020 at 16:39
  • VMDK is a container file for virtual hard disks. It is not the same thing or comparable to an ISO. The virtualized OS treats it like a hard drive, and the Hypervisor treats it like a virtual hard disk. To "reuse" it you treat it like a hard drive, except in virtual form.
    – music2myear
    Jan 12, 2020 at 0:40

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A VMDK is a file that VMWare uses to present a fake hard drive to an OS within a VM. It's essentially the contents of a hard drive stuffed in a single file.

The VMDK will be modified as the OS writes to the disk. It will contain all the files of a running OS, as well as applications, temp files, user files, etc.

An ISO is essentially the contents of a CD or DVD ROM stuffed in a single file.

It's not designed to be modified in the same way as a VMDK since CDs/DVDs are read-only.

VDMK's contain more than an OS and aren't really equivalent to an .ISO.

VMWare and other virtual machine suites will use .ISO files to present a fake CD or DVD ROM to an OS within a VM.

The question you're asking is similar to asking about differences between the data on a Windows install CD/DVD and the files on a hard drive where Windows is installed. The two are normally separate things and Windows is only copying files from the CD/DVD to the hard drive during installation. Nothing changes because this is done in a VM, it's just that the VM presents two virtual devices to the contained OS, using data from two separate files (ISO->virtual CD, VMDK->virtual HDD).

VMDK's may be distributed by vendors to allow people to try out OSes and/or various software. This is equivalent to them installing an OS and other programs on a hard drive then shipping you the hard drive, and you plugging into your own computer.

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  • So my VM will be based on the VMDK OS but adapted during 'installation' to recognize my video, audio, etc? The ultimate effect is the same as if I installed from an ISO?
    – Keith
    Jan 10, 2020 at 17:02
  • The adaptation you're talking about is the responsibility of VMWare, not the OS installed within a VM in most cases. VMWare converts from real hardware to the virtual hardware inside the VM. If the VM is setup properly it doesn't have to be concerned with the real hardware at all.
    – LawrenceC
    Jan 10, 2020 at 17:08

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