VirtualBox works good when you use the same VMs all the time. It organizes the disk images in one directory and the configuration files in another. It kees a record of all known disk images and virtual machines.

If you try to carry a VM around with you on an USB stick or want to put it on an encrypted image, then you will get trouble.

First thing is, that you have to be careful when creating the disk image and use the button to select the directory for the disk image or VirtualBox will put it in the default directory.

Second, you don't have an option to specify where to put the VM itself (it's a XML file). It will always be in a subdirectory under the machines directory.

At last, VirtualBox will remember the VM and the associated disk image and complain when they are missing.

To ease the handling of “moveable” VMs, I created a script which creates a VM and a disk image in a given directory and also creates scripts to activate and deactivate the VM.

So let's have a look at the script. I'll go thought some snippets here, but there is a link to the full script below.

At the top, there are two settings which you may want to change if you use the script. The VBOX= setting contains the full path to VBoxManage, VirtualBox's command line tool. SCRIPT_EXT= is the extensions for the generated scripts.

VBOX="/usr/bin/VBoxManage"
SCRIPT_EXT="command"

Next, there are defaults for the VMs parameters in case the user enters no value.

RAM="512"
DISK_SIZE="8196"
DISK_TYPE="vdi"

The script asks for the parameters and uses the defaults if no value is entered. For example, the question for the disk size:

echo -n "Enter disk size in MiB [${DISK_SIZE}]: "
read a
DISK_SIZE=${a:-${DISK_SIZE}}

The main part. The base directory, the VM and the disk image are created. The VM is configured according to the parameters above.

mkdir -p "${VM_DIR}"
 
${VBOX} -q createvm --name "${VM_NAME}" --basefolder "${BASE_DIR}"
${VBOX} -q registervm "${VM_DIR}/${VM_NAME}.xml"
${VBOX} -q storagectl "${VM_NAME}" --name "IDE Controller" --add ide
${VBOX} -q createhd --filename "${VM_DIR}/${VM_NAME}.vmdk" --size "${DISK_SIZE}" --format VMDK
${VBOX} -q modifyvm "${VM_NAME}" --hda "${VM_DIR}/${VM_NAME}.vmdk"
${VBOX} -q storageattach "${VM_NAME}" --storagectl "IDE Controller" --port 0 --device 1 --type dvddrive --medium emptydrive
 
test ! -z "${RAM}" && ${VBOX} -q modifyvm "${VM_NAME}" --memory "${RAM}"

Finally, the scripts are created. There are three of them: activate, boot (same as activate, just with an additional boot command) and deactivate. The variables are evaluated while creating, so the following code will create the activation script below.

Code:

cat << __SCRIPT__ > "${VM_DIR}/activate.${SCRIPT_EXT}"
#! /bin/sh
 
${VBOX} -q registervm "${VM_DIR}/${VM_NAME}.xml"
${VBOX} -q modifyvm "${VM_NAME}" --hda "${VM_DIR}/${VM_NAME}.vmdk"
${VBOX} -q storageattach "${VM_NAME}" --storagectl "IDE Controller" --port 0 --device 1 --type dvddrive --medium emptydrive
__SCRIPT__

Result:

#! /bin/sh
 
/usr/bin/VBoxManage registervm "/local/temp-vm/temp-vm.xml"
/usr/bin/VBoxManage modifyvm "temp-vm" --hda "/local/temp-vm/temp-vm.vmdk"
/usr/bin/VBoxManage -q storageattach "temp-vm" --storagectl "IDE Controller" --port 0 --device 1 --type dvddrive --medium emptydrive

You can have a look at the code either in the version as of this article or in the latest version. Please keep in mind that not all written here may be true for the later as the script will be improved in the future.

There are some things, which not yet work as I want them to.

• The VM must not have snapshots.
• You have to shut down the VM. If you suspend it, it won't detach.
• As the DVD drive is removed and recreated, the VM won't remember the mounted image.

If you found this script useful, please let me know (you can use the contact form or leave a comment). You can also subscribe the further blog postings of follow the changes to my scripts collection on bitbucket.org.