Virtualbox - writethrough disk not discarding changes

[clareq]

I'm trying to set up a VirtualBox solution for Computing classes to program. I've created my image, worked out how to provide access to their home folder without giving network access and all looks good. However, I want to start with a clean image every time - reading up on it I think writethrough suits my needs more than immutable - I don't want the snapshots created, just no changes kept. I've therefore changed the disk type - I've tried it via the command line and the GUI, but when I open the VM and save a file to desktop, it is still there after closing down the VM and restarting it. Just in case my understanding of writethrough was incorrect I tried immutable, same results.

 

What am I missing? All I want is a VM that students can use to program, without creating an environment where they can share their games ("I've saved zombies on the desktop of that machine, log on any you'll get it" type of thing)

[clareq]

Bump - help please guys...

[Sheridan]

I know this is an old thread, but I'm having the exact same issue with Virtualbox. Nice simple clean VM that was created with a writethrough drive so it boots up the same every time, but its simply retaining any changes made.

 

I used to use VBox on Xp a couple of years ago in the same way and it worked fine - in fact it worked brilliantly. Is it no longer possible to do this, or is vbox broken?

 

I've tried manually setting the drive to autoreset as well, but its had not effect.

[madurham]

I had the same/similar problem. Here's how I fixed it: http://www.edugeek.net/forums/thin-client-virtual-machines/140855-virtualbox-immutable-drive-problem.html

[Sheridan]

Ah that seems to work much better, its turning autoreset on for the differencing file that sorts it out!

[Sheridan]

Actually, this works but as soon as I move it to another PC it fails with a non specific error. It looks like a proper read-only VM doesn't exist for VirtualBox or MS VirtualPC so I'll just have to let them break it!

[peterp]

Why writethrough disks as opposed to immuatable?

I've got virtualbox with the VM's set to immuatable, and never have any issues with people managing to persist data between sessions.

It's also fairly easy to unattach the vdi, make it normal, re-attach, update the machine, unattach, set it to immuatable and reattach. Then wait the several hours it takes to deploy the 30gig immage to 30 machines :-)

 

Is there a benefit to writethrough?

[madurham]

I was using immutable before and it worked great, really simple. Then I created an updated VM and the immutableness was no longer working so I had to use the workaround in my link above. Oracle changed how immutable drives worked and I think this is what caused the problem I had. I've never used writethrough myself.

 

Sorry @Sheridan, I've not encountered that issue. We deploy virtualbox through SCCM and then through a second package deploy the VM folder with all the images within. As long as the .vdi, .vbox, and the Logs and Snapshots folders are there it should work fine.

[Sheridan]

I think it must version dependant now - immutable and writethough still allow changes to be persisted, unless (as madurham has mentioned) you use autoreset on the differencing file.

 

If I simply set the disk to immutable, changes are persisted, this is on Vbox 4.3.16

[peterp]

On vbox 4.3.16 I have our vdi's set immuatable and present the users with an icon to a batch file

 

"C:\Program Files\Oracle\VirtualBox\vboxmanage.exe" registervm "C:\VM\ProgrammingEnvironment\Programming.vbox"

"C:\Program Files\Oracle\VirtualBox\vboxmanage.exe" setextradata "C:\VM\ProgrammingEnvironment\Programming.vbox" GUI/SuppressMessages remindAboutAutoCapture,remindAboutMouseIntegrationOn,showRuntimeError.warning.HostAudioNotResponding,remindAboutGoingSeamless,remindAboutInputCapture,remindAboutGoingFullscreen,remindAboutMouseIntegrationOff,confirmGoingSeamless,confirmInputCapture,remindAboutPausedVMInput,confirmVMReset,confirmGoingFullscreen,remindAboutWrongColorDepth

"C:\Program Files\Oracle\VirtualBox\vboxmanage.exe" setextradata global GUI/RestrictedGlobalSettingsPages General,Input,Update,Language,Display,Network,Extensions,Proxy

"C:\Program Files\Oracle\VirtualBox\vboxmanage.exe" setextradata "C:\VM\ProgrammingEnvironment\Programming.vbox" GUI/RestrictedRuntimeMenus Machine,View,Devices,Help,Debug

"C:\Program Files\Oracle\VirtualBox\vboxmanage.exe" setextradata "C:\VM\ProgrammingEnvironment\Programming.vbox" GUI/RestrictedStatusBarIndicators HardDisks,OpticalDisks,FloppyDisks,Network,SharedFolders,Features,Mouse,Keyboard

"C:\Program Files\Oracle\VirtualBox\vboxmanage.exe" setextradata "C:\VM\ProgrammingEnvironment\Programming.vbox" GUI/RestrictedCloseActions SaveState,PowerOff,Restore

"C:\Program Files\Oracle\VirtualBox\vboxmanage.exe" setproperty machinefolder "C:\VM"

"C:\Program Files\Oracle\VirtualBox\vboxmanage.exe" startvm "C:\VM\ProgrammingEnvironment\Programming.vbox"

 

This doesn't persist changes. If the base vdi appears in manager with a small triangle to the side, then copy the disk with vbox media manager, delete the original and copy it back again, this will remove the differencing and snapshots. The changes then do not pesist.