For my work on digital preservation it's important to have "golden"
disk images that are not corrupted by user action. In order to enable
this, I've added support for VHD virtual disks (especially snapshots !)
to the Linux and OS X versions of BasiliskII and SheepShaver.
The support uses the open source libvhd library which is part of xen,
available here:
http://www.xen.org/products/xen_source.html
The piece that's needed is libvhd which is in tools/blktap2 and it can
be separately compiled.
The vhd-util enables creation of vhd disks and snapshots.
Compiling libvhd for OS X is non-trivial and required 1) a new config
and 2) a number of small changes to the include files and c files.
Compiling for linux is a snap.
I use this as follows.
1) create my "golden image" gold.dsk in the usual way
2) create a snapshot: vhd-util snapshot -n gold.vhd -p gold.dsk -m
3) use the snapshot in my prefs file
In my work the golden images are in an AFS system which means the golden
images can reside at "universal" addresses. The snapshots are initially
tiny, so a complete virtual machine configuration -- prefs + snapshot is
quick to download for the end user.
The snapshots are copy on write which has the pleasant side effect of
letting the end user keep any changes.
