Migrating VMs v3 layout to v4

[Warta]

Hello,

I would like to migrate from v3 to v4 and convert my VMs v3 layout to v4.

In the user manual (§ 10.1.2), it's said that old VMs "will not be converted for maximum compatibility",
to avoid problems if a user downgraded back to v3.

I noticed that, but in my case there's no risk to downgrade.

Is anybody's knows a way to convert VMs v3 layout to v4 ?

Thanks

[kidault]

I have not download the V4. Are you talk about this new feature?
"New settings/disk file layout for VM portability; see chapter 10.1, Where VirtualBox stores its files, see the manual for more information "

It seems that the v3 or v4 VM layout will not affect VM performance. V4 layout just make a VM's setting more portable.

And if you really want to do this, I have one suggestion. Set up a new maching in VB4 with the same hardware settings as your V3 VM, then attach the vdi file to the new machine.

[Warta]

Thanks for your answer Kidault.

My concern is not about performances. I just want to avoid having both V3 and V4 layout VMs but only V4. If I attach a V3 vdi to a V4 VM, it will remains in V3 layout (ie : all vdi located in the same folder) without any portability ...

[ChipMcK]

Been using VB for about two years and I have been using the VB 4.0 layout after the first month.
Yes, it was tedious to set up - release the virtual disk, move it, re-attach it.
I found the back-up and recovery of the vm easier, but otherwise, no big deal
Good Holidays!

[Croccydile]

Is there a way to preserve snapshots when doing this?

[marco]

It looks quite strange to me that the developers have not suggested any ways of doing such a migration.

Most people upgrading to VB4 have, obviously, some already created VMs which they are regularly using (with snapshots, saved states and so on) and they surely intend to carry on using them, otherwise they wouldn't upgrade.
The typical "upgraded" scenario, some weeks after the release of VB4, will be: VBox 4 with (maybe) some new VMs and (surely) multiple old ones, resulting in a mix between the old layout and the new one.

Such a mix does not involve any technical problems or issues, that's all right, but the desire of getting rid of it, achieving an uniform configuration and also having the old (and probably most used) VMs become less "old" and more portable thanks to the new layout is quite predictable, in my opinion.

Let's hope to have soon some advice on this matter, so that the migration can be somehow accomplished. After all, there is no need of something automatic or super-easy (the operation has only to be done once); an "official", reliable and not too complicated procedure would be perfect.

[Croccydile]

Well perhaps I should clarify the question as well.

I have a couple of VMs that have multiple snapshots but I don't think there is a reliable way to back up snapshotted VMs even with exporting them. (Am I wrong?)

If the new V4 format retains information for snapshots stored in the machine folder or such, to where I can import them with snapshots would be quite nice. In that way I could just eventually convert my VMs to the new format and just backup the machine folder then with the info file. I guess I will have to test this.

[Perryg]

I would not suggest that you try to move existing guests to the new "layout" if you have snapshots. The way that the previous control scheme compared to the new one is just too different. You might be able to but you more than likely will loose the snap shot and even the ability to start the original guest.

I converted all of mine one at a time but did not have snap shots (I don't use them for various reasons this one is just another example).

[marco]

...I converted all of mine one at a time but did not have snap shots (I don't use them for various reasons...

You did not have saved states either, I suppose.
Anyway, did you actually convert them or did you just "convert" them by manually creating new VMs with same settings and attaching the existing vdi files to them?

Apart from this, I still think many users would greatly appreciate the existence of some "official" way of migrating without being forced to choose between loosing their VMs' history (snapshots) OR keeping a somehow messy mix of the two layout schemes.
Your choice not to use snapshots is obviously quite respectable, but for many other users snapshots are actually one of the most interesting and useful features of virtualization. Not using it at all is somehow like riding a comfortable and silent car without ever switching it's 6 speakers hi-fi system on.

[Croccydile]

Well I did not intend to make a big fuss over this.

The main question would be, when using the new layout with snapshots... if you backup the machine folder (with snapshots) would it preserve the snapshots if you were to re-import it later?

[marco]

...if you backup the machine folder (with snapshots) would it preserve the snapshots if you were to re-import it later?

Well, I would definitely expect so.
It should be one of the main reasons why the new layout was conceived.

By the way, another question comes up:
how do we "import" a VBox4 VM coming from a backup or from another computer?
Just putting it's directory together with the others, inside the “VirtualBox VMs” folder?
What happens if the two computers substantially differ in hardware configuration?

[abcuser]

how do we "import" a VBox4 VM coming from a backup or from another computer?
Just putting it's directory together with the others, inside the “VirtualBox VMs” folder?

Machine | Add

What happens if the two computers substantially differ in hardware configuration?

How different? It should be working unless there is some 3d support that is supported by one hardware and not supported by other.

[marco]

Actually I did not notice the Machine->Add command.
I also didn't find anything about it in the User Manual, which seems to totally forget telling the user how to take advantage of the new layout's benefits in terms of portability, actually porting a VM's folder to another host.

I made some experiments porting some Linux VMs (in saved state) from a Win7-32 host to a WinXP-64 one and I had only some minor problems. The saved states were lost because the VMs' setting files (*.vbox) contained full path information about some ISO images; as those paths were not correct in the new host, VBox refused to open the VM. I had to manually remove those rows from each setting file.
Curiously, shared folders, despite having an equivalent issue (the paths stored in the setting files where also "wrong" for the new host) did not cause any similar problem.

[barefootguru]

I've been watching this topic for a while hoping for an upgrade to bring a 'convert' option, but finally developed a workaround while renaming a .vdi to keep it in sync with a changed machine name.

I used this post for inspiration http://www.trimentation.com/wp/?p=137

1. Shutdown the machine in question
2. Release the .vdi using the Virtual Media Manager
3. Clone the old drive (don't know if the full path is necessary):
VBoxManage clonehd /path/to/old/drive.vdi /path/to/new/inside/folder/drive.vdi --format VDI
4. In the machine's Storage settings, attach the new drive
5. Check it works
6. Delete old drive
7. Remove old drive from Virtual Media Manager

Note the machine XML files have different extensions (.vbox vs. .xml) but haven't worried about that.

Cheers

[mpack]

@barefootguru: dangerous advice. I see no clear sign that you considered snapshots. I also see no sign that this procedure actually results in a v4 layout! ISTM to me all you have done is unmount and then remount a drive in the same VM. The new drive will be whereever you put it, but simply having a drive outside the HardDisks folder is not the essence of the v4 format.

The essence of the v4 format is that the xml and the hard disk images are all contained within one folder, and the xml contains its own local media registry, which contains relative filenames hence allowing the folder to be copied or renamed.