How do I increase the hard disk size of the virtual machine?

Since VirtualBox 6, you can use the GUI, as per lenooh's answer.

Otherwise, open a terminal and navigate to the folder with the VirtualBox disk image, then use the following command:

VBoxManage modifyhd YOUR_HARD_DISK.vdi --resize SIZE_IN_MB

replacing YOUR_HARD_DISK and SIZE_IN_MB with your image name and desired size. sudo might be necessary in some machines or you might encounter an error. This answer and a fuller explanation are here, on webupd8. Credit to Andrew there for posting this answer.

After resizing, the extra virtual hard drive space needs to be partitioned and formatted for the guest to use it. This can be done with gparted by booting the guest from a live ISO. We can also resize the existing partition using gparted. For this we may need to disable /swap and create a new swap partition.

In case if VBoxManage is not found in your system, just set the path to:

set PATH=%PATH%;"C:\Program Files\Oracle\VirtualBox" 

and it should resolve path issue. Do make sure VBoxManage is present at this path before setting it.

Since VirtualBox 6 we can use a GUI for resizing VMs' virtual disks.

To access it, click File -> Virtual Media Manager ...

The following window will open

Select your disk, and click Properties. Now just move the slider at the bottom or write the value you want for the size and click "Apply" when you’re done.

After you start the virtual machine, Windows will not recognize the new space.

In Windows, open Computer Management (search for it in the start menu), select Storage -> Disk Management in the left menu (In Windows 10 you can find it as create and format hard disk partitions directly from the start menu). Select your partition (probably C:), right-click on it, and select Extend Volume .... Now just click through the wizard and you're done.

Note that on your VM Windows might not detect the extra space if you have snapshots in your VM. To fix this, it is recommended that you delete the snapshots or (the easiest way) just clone it and perform the resize in the new one.

The following worked for me:

VBoxManage modifyhd YOUR_HARD_DISK.vdi --resize SIZE_IN_MB

However, I understand how mileage can vary :-) As far as resizing the partition, in Windows 7, I was able to resize at the screen you showed by right clicking on the C: drive in the bottom panel and selecting extend volume.

Wim, I think you'll need to unregister it from Vbox first. File, Media Manager, Click on you hdd, and unregister it. Then try it again.

If you are on Windows host and trying to increase the size of Ubuntu's VDI size then the following information can help you:

Get your full path of vdi, for me, it was "D:\VirtualBoxImages\Ubuntu\Ubuntu.vdi".

Run the command mentioned in the "Marked as answered" post:

"C:\Program Files\Oracle\VirtualBox>VBoxManage modifyhd D:\VirtualBoxImages\Ubuntu\Ubuntu.vdi --resize 40000" 

Above, "C:\Program Files\Oracle\VirtualBox" is the location of the folder where my Windows Virtual Box is installed, 40000 is 40 GB in the above command.

After doing the above-mentioned step, restart the Ubuntu VM.

Go to "Disks"

Resize the existing partition to make it 40 GB:

You can then confirm from the "Storage" that the above operation worked:

After resizing and not being able to view the resizing on my windows XP guest machine, I had to

1. clone it
2. resize it with "VBoxManage modifyhd winxppro\ Clone.vdi --resize 30720" and everything worked

I saw in other forums that snapshots can interfere for resizing and not being able to remove all snapshots for different errors I got, the only found solution for me was to clone it to remove the snapshots and then resize it, and everything worked. For resizing outside windows, a gparted boot cd that can be found here can help

I had the same problem where I had moved a disk, and replaced the original with a symlink. This works OK afterwards, but you run into problems with the 'modifyhd' command, as that apparently canonicalizes the path to the vdi-file when working with it. This makes it looks like you're trying to add a new disk with the same UUID but on a different path - or something like that.

There was two problems:

1. The disk had to be removed from the VM that used it, but then also "from the VirtualBox list of hdds". This was fixed with 'closemedium' command, which removes it from that list.

2. The disk to be resized was a "fixed disk" instead of "dynamic", and only dynamic disks can be resized. That was fixed with a 'clone' command (the clone is dynamic), and then resize the resulting disk.

This is my log for how it was done. Do notice that I am not at any point running as root, except when I afterwards do the resize of the partition and filesystem.

REMOVE THE ASSOCIATION TO THE DISK FROM VM.

PROBLEM STILL PERSISTS:

virt_box@TestBox:~/VirtualBox VMs/TestInception 64 bit$ VBoxManage modifyhd TestInception\ 64\ bit.vdi --resize 8192
VBoxManage: error: Cannot register the hard disk '/datadisk/VirtualBox VMs/TestInception 64 bit/TestInception 64 bit.vdi' {6cd99209-e4db-4178-a6c2-53f9581b1fad} because a hard disk '/home/virt_box/VirtualBox VMs/TestInception 64 bit/TestInception 64 bit.vdi' with UUID {6cd99209-e4db-4178-a6c2-53f9581b1fad} already exists
VBoxManage: error: Details: code NS_ERROR_INVALID_ARG (0x80070057), component VirtualBox, interface IVirtualBox, callee nsISupports
VBoxManage: error: Context: "OpenMedium(Bstr(pszFilenameOrUuid).raw(), enmDevType, enmAccessMode, fForceNewUuidOnOpen, pMedium.asOutParam())" at line 178 of file VBoxManageDisk.cpp

Ah, the disk is still "in the system":

virt_box@TestBox:~/VirtualBox VMs/TestInception 64 bit$ VBoxManage list hdds
UUID:        ba58276a-bbe1-4354-8ae5-246bdac390c8
Parent UUID: base
Format:      VDI
Location:    /home/virt_box/VirtualBox VMs/TestInception 32 bit/TestInception.vdi
State:       locked write
Type:        normal
Usage:       TestInception 32 bit (UUID: a693ac62-7caa-4f11-9d00-51d3a149f5f7)

UUID:        6cd99209-e4db-4178-a6c2-53f9581b1fad
Parent UUID: base
Format:      VDI
Location:    /home/virt_box/VirtualBox VMs/TestInception 64 bit/TestInception 64 bit.vdi
State:       created
Type:        normal

Remove/delete the disk from the VirtualBox disk list ("closemedium"):

virt_box@TestBox:~/VirtualBox VMs/TestInception 64 bit$ VBoxManage closemedium disk 6cd99209-e4db-4178-a6c2-53f9581b1fad
virt_box@TestBox:~/VirtualBox VMs/TestInception 64 bit$ VBoxManage list hdds
UUID:        ba58276a-bbe1-4354-8ae5-246bdac390c8
Parent UUID: base
Format:      VDI
Location:    /home/virt_box/VirtualBox VMs/TestInception 32 bit/TestInception.vdi
State:       locked write
Type:        normal
Usage:       TestInception 32 bit (UUID: a693ac62-7caa-4f11-9d00-51d3a149f5f7)

Try the resize again:

virt_box@TestBox:~/VirtualBox VMs/TestInception 64 bit$ VBoxManage modifyhd TestInception\ 64\ bit.vdi --resize 8192
0%...
Progress state: VBOX_E_NOT_SUPPORTED
VBoxManage: error: Resize hard disk operation for this format is not implemented yet!

DAMN, "fixed-size" DOESN'T WORK! 'clonehd' to the rescue, as that leaves a 'dynamically allocated' cloned disk:

virt_box@TestBox:/datadisk/VirtualBox VMs/TestInception 64 bit$ VBoxManage clonehd TestInception\ 64\ bit.vdi TestInception\ 64\ bit-cloned.vdi
0%...10%...20%...30%...40%...50%...60%...70%...80%...90%...100%
Clone hard disk created in format 'VDI'. UUID: 8e237500-173b-401a-9e63-9e64da110da9

NOW DO THE RESIZE (instantanious):

virt_box@TestBox:/datadisk/VirtualBox VMs/TestInception 64 bit$ VBoxManage modifyhd --resize 8192 TestInception\ 64\ bit-cloned.vdi 
0%...10%...20%...30%...40%...50%...60%...70%...80%...90%...100%

THEN ATTACH TO SOME VM, FOR RESIZING. This is done as root. Assumes that you only have one partition and possibly swap.

# fdisk /dev/sdb  # <- The extra disk, just attached to be resized
// The procedure looks like this:
// m - print help
// p - print table
// d ... - delete partition (delete both if you have root and swap)
// n - new partition (create root/first partition starting on exact same sector as before, typically 2048, but ends on last, or last minus swap)
//  ... n.. (.. then add the swap partition. Calculate how many sectors using original table)
// t - change type of partition (swap partition, if any, to 82 - not 83 which is "normal Linux").
// w - write partition table (write out, with the resized partition)

# e2fsck -f /dev/sdb1

e2fsck 1.42.5 (29-Jul-2012)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/sdb1: 99918/122160 files (0.3% non-contiguous), 471032/487936 blocks

# resize2fs /dev/sdb1

resize2fs 1.42.5 (29-Jul-2012)
Resizing the filesystem on /dev/sdb1 to 1965824 (4k) blocks.
The filesystem on /dev/sdb1 is now 1965824 blocks long.

This worked for me with Virtualbox 5.2.6 installed on Ubuntu 16.04 Host Machine and Windows 10 Guest: open Virtualbox Manager, click on Global Tools (upper right corner) and choose Virtual Media Manager. Click on the Hard Disk Tab and select your Guest OS. At the bottom of the box click on the Attributes Tab. At the bottom you can see the size of the Virtual Disk, and with the slider you can increase the size to your liking. (You can only increase, not decrease the size with this method). Click on Apply. Start your Windows Guest OS, open Computer Management, right click on the C: Drive, and select Extend Volume to extend the file system with the unallocated part.

That’s all I had to do, works perfectly for me.

Here's a way to resize your VirtualBox disk, regardless of whether it is a fixed format or dynamic format disk. Specifically, it prevents this error:

Progress state: VBOX_E_NOT_SUPPORTED
VBoxManage: error: Resize hard disk operation for this format is not implemented yet!

⚠️ Backup the virtual disk. You never know what might go wrong.

On your host:

1. Open a terminal window.

   On Windows: Open the command prompt cmd.

2. Go to the directory with the virtual disk you want to resize. For example:

   cd "My VMs"
   

3. Create a new VirtualBox disk with your desired filename, size (in megabytes) and format (either Standard (dynamic) or Fixed). For example, to create a 50 GB fixed-format disk called MyNewDisk.vdi:

   VBoxManage createmedium --filename "MyNewDisk.vdi" --size 50000 --variant Fixed
   

   If VBoxManage is not recognized as a command, specify the full path to it. It can be found in the VirtualBox installation directory. On Windows the above command would become:

   "C:\Program Files\Oracle\VirtualBox\VBoxManage.exe" createmedium
       --filename "MyNewDisk.vdi" --size 50000 --variant Fixed
   

4. Copy the original disk to the new disk.

   VBoxManage clonemedium "MyOriginalDisk.vdi" "MyNewDisk.vdi" --existing
   

5. The resize is done! You can check the properties of the new disk if you want:

   VBoxManage showmediuminfo "MyNewDisk.vdi"
   

6. Change the virtual machine to use the new disk instead.

Next, on your guest OS you need to resize the partitions to use the newly available space.

A sure-proof way is to do it the same as moving to a larger hard drive that's not running in a VM. First use ccleaner or similiar program in XP to clean up all junk files that it can. Then create a secondary virtual HDD of the size you want. Boot with the clonezilla ISO in your virtual ODD drive and clone over along with the 'resize to new partition size' option selected. Then set the new Virtual HDD as primary, and don't delete the old one until you know it worked.