Shrink a Ubuntu Guest VDI File

When using a Ubuntu virtual box guest, sometimes we want to shrink the dynamic expanding VDI file to release the unused disk space. Here is the steps to archive that.

1. Install ZeroFree

   sudo apt-get install zerofree

2. Reboot into recovery mode
   a. sudo shutdown -r now
   b. Holding the left Shift key while rebooting
   c. Select Advanced and then Recovery mode and finally Drop to root shell prompt option.

3. Remount the root partition

   mount -n -o remount,ro -t ext4 /dev/sda1 /

4. Run ZeroFree

   sudo zerofree -v /dev/sda1

5. Shutdown the VM

   shutdown -h now

6. Shrink the VDI file is host OS

   SET PATH=%PATH%;"c:\Program Files\Oracle\VirtualBox
   VBoxManage modifyhd Ubuntu.vdi -compact

   
   

Reference: How to shrink a dynamically-expanding guest virtualbox image