VirtualBox Notes

Backing up

Just make a copy of the .vbox and .vdi files.

Reducing disk space of dynamic disks.

This doesn’t work for encrypted disks.

On client virtual machine:

  • For Windows
    • Defragment disk, e.g defrag c:
    • Zero free space, e.g sdelete -z c: (sdelete is part of SysInternals)
  • For Linux
    • dd if=/dev/zero of=zeroes bs=1M until there is no space left
    • rm zeroes

Followed by on host computer:

  • VBoxManage.exe modifyhd /path/to/file.vdi --compact

Alternate technique

It may help to defragment and zero free space on existing disk first.

  • Create new VDI of smaller size.
  • Boot GParted or Clonezilla using ISO image, and clone existing disk to the new smaller sized disk (vdi).
  • Change VM settings and boot VM using smaller disk.

Sharing a folder RHEL or CentOS Linux VirtualBox VM

Update VirtualBox Guest Additions modules

Requires gcc and kernel headers installed. If not then run:

yum instal -y gcc kernel-devel-$(uname -r)

Devices > Insert Guest Additions CD image

mount /dev/cdrom /mnt
sh /mnt/VBoxLinuxAdditions.run
umount /mnt

Check module is installed with lsmod | grep vbox. You should see the vboxsfmodule.

Sharing a folder

To attach a folder for sharing:

  • Under Device > Shared Folders – Add your desired folder. Select “permanent” if you want this folder shared all the time.
  • Mount the drive with: mount -t vboxsf FOLDERNAME MOUNTPOINT
  • When finished, umount MOUNTPOINT

To make mount point persistent between reboots, add entry in /etc/rc.local (or /etc/fstab).

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