Linked clone changes persist only if clean shutdown of guest

[GaryCharles]

Virtual Box 4.2.6 is running on Debian 6.0.

I have a base Windows XP machine and in Media Manager I made the disk Immutable. Then I never touch it again and make linked clones from that vm.

I can be using the clone for days and making changes to the linked clone guest all along. As long as the clone gets shutdown properly the changes continue to persist through the life of the clone and through reboots of the guest OS. If something happens in the clone so that they are not shutdown properly, the clone reverts back to very first state it was in right after creating it. So I lose all of the changes made during the life of that clone.

I searched but wasn't able to find this reported before. Has anyone heard of this or have ideas?

Thanks,
Gary

[mpack]

If you make a disk immutable in VM-A then there is already a differencing disk attached to A. If you create a linked clone B then it is differenced from A's differencing image, not from the original immutable disk. So VM-B is at the end of a chain of differencing disks, the head of which is marked in the registry as immutable... the effect of which I'm not altogether sure of. It doesn't sound like the most robust of structures to me.

Why do you believe that you need this arrangement? If you are worried about modifying the original VM, why not simply make a backup copy of it?

[GaryCharles]

mpack thanks for your reply. I thought the immutable setting would prevent changes to the base(VM-A in your example). Typically I make a bunch of changes to the base and get it just right then never touch it again. I could make a backup as you suggest but I didn't want to eat up disk space. I was trying to avoid using lots of disk space with the linked clones.

I must be using the immutable setting wrong.

Even after reading the(I'm too new to post full urls) www_virtualbox_org/manual/ch05.html#hdimagewrites Special image write modes section.