Re: [Libguestfs] virt-sysprep future

On Mon, Mar 26, 2012 at 03:59:04PM +0800, Wanlong Gao wrote: > I'd like to know when will you work out the virt-sysprep in Ocaml ? :-D I meant to write something about our investigations last week. Here we go ... Requirements: * Compatible with the current virt-sysprep, but easier to maintain and faster. * It should work in the "local" and over-libguestfs cases, which means using FUSE. * The current version is a shell script, so it's customizable by simple editing. I'd like to keep some customizability in the new version.

These requirements could all be satisfied if we had: * Some kinds of "mount-local" ability, ie. integrating FUSE with the API in some way. [i] * Custom scripts: virt-sysprep --script foo.sh # runs foo.sh on the guest

The problem is how to do the "mount-local". We analyzed this last week on IRC and came up with two possible methods: (1) We add FUSE support directly to the API, linking with libfuse. This is essentially the same as what was outlined in link [i] back in December 2011. (2) We add an attach-method "fd:<N>" which allows the file descriptor of the appliance to be passed over to another process. In this case we would allow guestmount to be passed a file descriptor (eg. "guestmount --attach-fd=<NN>") which it would then use exclusively.

The problem with (1) is that we are not confident that it's a good idea to use libfuse as a true library. It doesn't appear that anyone else is using it this way. The problem with (2) is that it's complex and isn't future compatible with remote libvirt support [ii]. I suspect that we'll need to implement both, and be prepared to throw away a few implementations, before we know really which is the best way to go about this. Rich. [i] https://www.redhat.com/archives/libguestfs/2011-December/thread.html#00136 [ii] https://www.redhat.com/archives/libvir-list/2011-September/msg01049.html