How To Extend VirtualBox Dynamic Disk For Windows Server 2012 R2

I wanted to set up a lab environment using VirtualBox to test SQL Server 2016.  I  first started with the installation of Windows Server 2012 R2 and 15GB space configured as dynamic disk.  Installation went smooth and I then started the windows update process. After a while I started getting low disk free space and updates failed.  Here are the steps I took to extend the disk and screenshots below them.

1. Shutdown the virtual machine that needs additional space
2. Open up a command prompt with administrator privileges
3. Change your folder path to where VirtualBox is installed
4. Type the command above the first screenshot and provide the full path of the virtual disk you want to extend and the size you want to extend  the disk to, command provided below extends  the dynamic disk to 20GB
5. Start the virtual machine and log in  to windows
6. Open the 'Computer Management' and under the 'Storage' section on the left side of the pane and click on 'Disk Management' and you will see the unallocated space for the disk you just extended using the command in step  4
7. Right click on the disk you want want to extend to bring up the context menu where you will see 'Extend Volume' option
8. Click on 'Extend Volume'
9. This will bring the 'Extend Volume Wizard' and follow the steps in the wizard

VirtualBox command to extend the dynamic disk:
vboxmanage modifyhd "pathToYourVHDfile" --resize 20480

And here are the screenshots.

 

 

HTH,
Bulent