[Libguestfs] Standalone guestfs

[Gabriel de Perthuis]

> On Sat, 01 Jun 2013 20:54:15 +0100, Richard W.M. Jones wrote:
>> On Sat, Jun 01, 2013 at 02:27:50PM +0000, Gabriel de Perthuis wrote:
>>> Hello,
>>> As I understand it guestfs appliances normally work as servers
>>> and run high-level commands from some external channel.
>>
>> This is the normal architecture when you're using libguestfs to access
>> a VM or disk image:
>>
>>   http://libguestfs.org/guestfs.3.html#architecture
>>
>>> But it might be possible to bundle a guestfish script to run
>>> commands from and do away with the external system.
>>> That would make it useful on non-virtualised systems.
>>
>> It's worth noting you can edit any device, including host devices
>> directly.  For example on my laptop:
>>
>> It's also possible to get libguestfs to connect to an arbitrary
>> socket, so-called 'libguestfs live'.  That could include a guestfsd
>> daemon running on the local host.  Run the daemon and set
>> LIBGUESTFS_BACKEND=unix:/path/to/some/socket
>>
>>   http://libguestfs.org/guestfs.3.html#backend
>>   https://rwmj.wordpress.com/2011/07/07/how-does-libguestfs-live-work/#content
>>
>> It would also be possible to run qemu-nbd or sshd on a physical
>> machine and access it using libguestfs (>= 1.22) from another machine.
>> Indeed this is a possible architecture under discussion for the new
>> version of virt-v2v.
>>
>> Hope that gives you some ideas.  If you have a specific use scenario
>> you are interested in, then please let us know.
>
> I was thinking of running some operations on the root filesystem
> by kexec-rebooting into an appliance to get exclusive access.
> I would like to do something like that for my blocks tool
> (which does conversions to LVM and bcache).
>
> https://github.com/g2p/blocks#readme

supermin + supermin-helper + blocks might be useful to get this to work
(or another image builder like Oz, but I haven't played with this much).
I'm not yet sure I should integrate with guestfs, but it might be useful
for VMs.  If so, libguestfs-live could be used in the kexec case.