Resizing Virtual drive [duplicate]

I am running Ubuntu as a guest on an iMac with VirtualBox version 4.1.8.

What is the easiest way to resize the virtual drive?

Please provide as much detail as possible including the correct format for any commands.

This answer is directed at a Windows host, but if you use bash in place of the PowerShell and replace '\' with '/' it should work just fine.

Enlarge virtual drive

1. From VirtualBox
   1. Release the VDI file: File -> Virtual Media Manager -> Select VDI -> Release
   2. Copy the location of the VDI inside the properties box 'C:\Users\campbell\VirtualBox VMs\Ubuntu14\Ubuntu14.vdi'
   3. Backup the VDI file
      1. Copy the VDI file to a new location.
      2. Assign a new UUID to the original VDI file:
         1. Start Powershell (not as an administrator):
         2. Change to your Oracle VirtualBox directory cd C:\Program Files\Oracle\VirtualBox
         3. .\VBoxManage.exe internalcommands sethduuid "C:\Users\campbell\VirtualBox VMs\Ubuntu14\Ubuntu14.vdi"
   4. Remove and re-add your machine's .vdi file to update its UUID.
      1. File -> Virtual Media Manager -> Select VDI -> Remove
      2. Apply.
      3. Right click your VM -> Configuration -> Storage -> Controller: SATA -> Add new hard drive. Select your .vdi file.
2. From host
   1. Work out desired size: you can google it, eg. '40 Gb=MB' returns 40000 MB
   2. Start PowerShell (not as administrator)
   3. Change to your Oracle VirtualBox directory cd C:\Program Files\Oracle\VirtualBox
   4. Resize your .vdi file .\VBoxManage.exe modifyhd "C:\Users\campbell\VirtualBox VMs\Ubuntu14\Ubuntu14.vdi" --resize 40000
   5. Now start your virtual machine. You will receive the same warning about space that prompted you to engage in this procedure. Not to worry, we are near the end.
3. On your virtual machine
   1. Start the partition manager gparted (install it if is is missing sudo apt-get install gparted)
   2. Get rid of the swap partition, which prevents you from expanding the root partition. Note that you cannot harm the rest of your machine - this is all happening inside a single file. Worst case scenario you trash this file and you have to use your backup instead.
      1. Make a note of the size of the linux-swap partition 4 GiB in my case
      2. Right click on it and Swapoff
      3. Right click on it and Delete
      4. Apply by clicking on the checkmark (Apply all operations). Ignore the dire warning - life is too short to indulge Cassandras
      5. right click on the extended file system that once housed the swap partition (/dev/sda2 in all likelihood) and delete it
      6. right click on the root partition (/dev/sda1) and resize it. Tab to the 'Free space following' field and enter the size of the swap partition. Shift-Tab and the machine will work out the new size for you automatically.
      7. Right click in the unallocated space at the end and make it an extended partition
      8. Right click in the new partition and select linux-swap in the File system field.
      9. Commit your changes as before
      10. Right click on your swap partition and select swapon
      11. Tell the Fat Lady to commence singing.

References:

1. https://tinyapps.org/blog/misc/201204120700_virtualbox_increase_disk_space.html
2. Resize Ubuntu 10.04 VirtualBox VM virtual disk

If you are making the disk bigger, you would

1. first enlarge the disk from VirtualBox, and then
2. enlarge the partition, and
3. the filesystem it contains.

To enlarge a disk you can use the VBoxManage modifyhd command. Suppose you want to resize the disk to 20,000 megabytes (~20GB). First locate the disk file that you want to expand. Then, in terminal, give this command to resize the disk:

VBoxManage modifyhd "path-of-disk-file" --resize 20000

To enlarge the partition and file system, probably it's easiest to boot the virtual machine using a Ubuntu livecd and do the job with GParted, as it does both at the same time and gives you a graphical user interface for it.

Attach a livecd ISO image to the virtual machine and change the boot order to first boot from CD. If you don't have a Ubuntu livecd at hand you can use any livecd that comes with the appropriate tools. SliTAZ for example is only 35MB to download. Open GParted and choose the disk you want to resize. Then right-click on the partition that you want to expand and choose the option "resize-move." In the dialog box that opens, in the graphic that represents the partition, drag the triangle at the end of the partition all the way to the right to maximize it. Then close the dialog and choose "Apply" on the toolbar. Since no data has to be moved this should be a quick operation.

When done, don't forget to detach the livecd from the virtual machine and change the boot order.

You'll find a pretty good tutorial of the whole process with screenshots included here: http://trivialproof.blogspot.com/2011/01/resizing-virtualbox-virtual-hard-disk.html