Update: There is a much easier way now to resize a virtual disk: Expand a virtual VMware disk with VMware Converter. Also check out this article about my first impressions of VMware Converter 3.0 final.

Today, my Windows XP test system running in a virtual machine under VMware Workstation 5.5 complained that there is not enough space anymore on the system partition. I thought it can't be too complicated to resize a virtual disk. After all, it is only virtual. I hoped to solve this problem within 5 minutes or so. Well, here's how it went:

I was disappointed the first time when I realized that one can't change the size of a virtual disk with the VMware user interface. So I googled this problem, hoping to find an easy-to-use tool. What I found out was that the virtual disk can be resized on the command line using the VMware Virtual Disk Manager Utility. The documentation about this feature on the web is for VMware Workstation 4.5, but it also works with version 5.5 and also for VMware GSX Server.

The command to expand a virtual disk looks like this:

vmware-vdiskmanager -x 10GB myDisk.vmdk

The new size of the virtual Disk will be 10 GB in this example. myDisk.vmdk is the file of the virtual disk on the host system. Usually this file won't be located in the same folder as vmware.exe. Thus, you have to specify the full path to the vmdk file. Don't forget to enclose the path in quotation marks, if the folder names contain spaces. You can find vmware.exe in the VMware installation folder.

My second disappointment was that one can't expand a virtual disk if it contains snapshots. With a heavy heart, I deleted all my snapshots of this virtual machine. I was surprised how much time VMware needed for this. The size of the disk was 4 GB and I had three snapshots. I didn't measure the time, but it must have taken at least 15 minutes. This is amazing considering that it only takes a few seconds to create a snapshot.

Finally, I was able to expand the virtual disk. The virtual disk manager needed several minutes to enlarge the virtual disk to a size of 10 GB. Of course, you can only do this after you shut down the virtual machine. It is recommended that you backup the vmdk file first, just in case something goes wrong.

I was disappointed the third time when the Virtual Disk Management Utility eventually finished its task. Expanding the virtual disk was successful, but the tool suggested using a third-party tool to resize the partitions within the virtual disk. So basically I was back to where I started. I, now, had a bigger virtual disk, but the system partition of my virtual machine still remained the same size.

Luckily, I remembered that I have an old version of Partition Magic. Since my virtual disk was full, I had to create a second virtual disk on this virtual machine first to get some free space for Partition Magic. I suppose, you know that one can add a new virtual disk by changing the virtual machine settings. Partition Magic 7.0 had no problems enlarging the system partition on my VMware virtual disk.

All in all, it took me about an hour to resize my virtual disk, including the search for a solution for my problem and the time to find my old Partition Magic. I guess I was a bit too optimistic with my five minutes estimation. I hope that future versions of VMware will offer more comfort here.

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  1. KYovev 11 years ago

    Hey there.
    Looks like there are a lot of people fasing same problems with disk sizes in VMWare.
    Here are my simple few steps for resizing the bootable disk in a virtual machine running win 2003.:
    My server info:
    HP DL 360 running VMWare ESX Server 3i
    HP MSA StorageWorks 2012i containing all system and data volumes.
    Here is it:
    1. Make sure you have enough free disk space to add later to the VM.
    2. Shut Down the virtual machine.
    3. Delete all snapshots of it.
    4. Using VM Infrastructure Client right click the VM you want to edit and click Edit Settings.
    5. Click on Hard Disk 1 and in the right pane increase the size of the disk.
    6. Hit OK and Power ON the VM.
    7. Now use a partition manager of your choise to add the unallocated disk space to your disk.
    8. Enjoy 🙂


  2. [...] base image you’d rather just expand what you have. No longer to you have to go through this old methodical process. Now you can use VMware Converter to do it for you through the UI. Very slick! (why this [...]


  3. John Croson 11 years ago

    Excellent. Saved me 45 minutes!


  4. RockOn 11 years ago

    Ran command: vmware-vdiskmanager -x 10GB myDisk.vmdk and then in Vista used the disk manager to extend to use newly allocated space and it all worked!


  5. [...] One piece of advice: I only allocated 3GB to my mage and that quickly filled up. You can increase the size of your VMWare image through a simple command line that is detailed here. [...]


  6. vdv 11 years ago

    Hi! help me. I've a ESX sever 3.5 and few virtual station with Windows server 2003. I want to expand size hard disk on VM, but I can't. This is what I'm doing in VMware Infrastructure Client:
    - Select a VM
    - Click on Edit Settings under Commands
    - On the Hardware tab, select Hard Disk [x]. Observe the text box next to New Size: and that it is possible to enlarge this size. Add a few GB and select OK.
    - I get an error like the following:

    A general system error occurred: Internal error

    At other times it will look like the disk has been resized, but going back into the Edit Settings dialogue simply shows the original size again.

    Any ideas?
    But in the other VM I can change size!


  7. vdv 11 years ago

    I solve problem. I remove all snapshots!


  8. Slavi 11 years ago

    I am receiving a strange error:
    Diskpart failed to extend the volume.
    Please make sure the volume is valid for extending...


  9. Kevin 11 years ago

    vdv is awesome! I was getting that same error and now I understand why. Now that I understand the reason, I am glad for it. In the past, if you forgot to clean out your snapshots before expanding a disk, you would revert to an earlier snapshot. That was really bad! It would be nice if the error message said 'you must clean out your snap shots' instead of 'general error' - but hay, I will take it!


  10. Petr 11 years ago

    You saved a lot time. Thanks for the nice manual - it went smoothly on my laptop.


  11. R1440_CO 10 years ago

    If you are using Windows 2008, you can simply edit the disk and make it larger in VMWare.

    Start the server, go into disk management, and extend the C volume to the extra disk! Done. One nice thing about 2008 server.


  12. Paul Evans 10 years ago

    Thanks for an insightful post, Michael. Judging by the activity on the comments, you have seeded a lively community around this topic.

    You should download and try fatVM http://www.gudgud.com/fatvm

    fatVM is a reliable, robust, and safe, 1-click solution for extending the C drive of your VMware Fusion or Workstation virtual disk that is becoming full.
    * It provides a simple, intuitive, interface and a reliable process that hides the technical complexity of extending a virtual disk.
    * It is robust because it can extend virtual disks having snapshots and clones.
    * It is safe because it preserves your original disk, which remains available to you for when the need ever arises.



  13. Stefano Frassi 10 years ago

    Thanks for your post, i resolved my disk full problem with these sw: VMware Virtual Disk Manager Utility (resize the vmdk) and partition wizard (resize my OS partition)

    ps: my config:
    vmware Server console 1.0.1 and vmdk os windows 2000 pro



  14. svdb 10 years ago


    vmware-vdiskmanager works great.


  15. Robert 9 years ago

    After using the vmware script to "Grod" the virtual disks in my GSX environment, I used the built in "Diskpart" utility to extend the non system volumes.


  16. Robert 9 years ago

    sorry for the fat finger, meant to type grow, not grod!


  17. Luis 9 years ago

    Thanks, saved me a lot of time.


  18. Chaan 9 years ago

    the vmware cmd line tool is a joke. The Aomei Partition assistant 3.0 has a disk extender tool that does it in seconds. Tried all sorts of tools before this one did exactly what I wanted it to which was extend the system partition without data loss, just drag the slider to have unallocated extended and et viola!!


  19. Logi 9 years ago

    Guys - This is very simple.

    First shutdown the machine, edit the virtual disk to be larger. Start the machine, go into computer management under administrative tools, right click on the volume you want to extend, press "extend", follow the instructions and you're done in 5 minutes.


  20. Jimi Sweden 9 years ago


    To clarify the Comment by R1440_CO

    If you edit disksize in ESXi when the windows 2008 server is running you will have to reboot the windows 2008 server before you can extend the volume in "Disk Management"



  21. vogelbsj 9 years ago

    I run virtual machine for XP Pro and have resized virtual disk.
    When I run admin tools I see the extra disk as a separate volume and don't see the extend option on either the whole disk or individual volumes.

    any thoughts?


  22. Genaro Giangan 8 years ago

    You can't expand system disk on your VM if you have snapshots. It will grayed out the Disk provisioning option. Delete all the snapshots and it all works!


  23. IVA Advice 8 years ago

    Problem solved, I also removed all snapshots


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