Re: [Libguestfs] Proposed changes for OpenStack

On 12/14/2011 10:36 AM, Richard W.M. Jones wrote: >On Wed, Dec 14, 2011 at 09:33:35AM +0000, Matthew Booth wrote: >>On 12/14/2011 08:44 AM, Richard W.M. Jones wrote: >>>[These two patches are for discussion only] >>> >>>Allow FUSE support to be used directly through the API. >>>This is the second commit. >>> >>>In order to make this usable from guestfish, we have to >>>also bind the events API in guestfish. This is the first >>>commit. >> >>There's not really enough information here to evaluate the proposed >>changes. Can you give an example of what you're trying to do? > >There's a very specific need for this in OpenStack. We want to be >able to inject files and make other filesystem changes -- and there is >already common code which assumes the guest filesystem is mounted >somewhere. But also we want to call libguestfs APIs such as >guestfs_tune2fs. Currently we can do the mounting bit by calling >guestmount, and we can do the other libguestfs API calls, but we need >to launch libguestfs twice to do this. > >Here is Padraig's current OpenStack patch: > >https://review.openstack.org/#change,1993 >https://review.openstack.org/#change,1994 Ok, it's an efficiency thing. However, I still think it's the wrong solution. What you really want to do is use 1 appliance for 2 things. We already have a mechanism to do that: ATTACH_METHOD_UNIX. Why not update guestmount to use it? >>In general, though, this feels wrong for a couple of reasons. >>Firstly, a callback mechanism implemented with shell scripts is >>simply hideous. Imagine trying to use that from another language. > >This is only for guestfish (which is a shell script tool). How would >you want to capture events in guestfish? Not quite so hideous, but I remain unconvinced. Use another language? That's not a flippant suggestion, btw. There comes a point in shell scripting when you're exceeding what it was designed for.