On Thu, Dec 20, 2012 at 04:00:10PM +0800, Wanlong Gao wrote: > Hi Rich, > > We just found that the libguestfs can't access the remote URI. > When doing guestfs__add_drive_opts(), we always add files from > local system, it's related the -c|--connect option. > > As I know, we are using local kernel to lunch the min-guest, > and it's hard to attach remote disks to our local min-guest. > > Our test team found this problem by using following command, > > # virt-sysprep -c qemu+ssh://<host>/system -d domname > > Then, for example the path of remote disk is /work/rhel.img, > but we are about to access the /work/rhel.img locally. > > So, IMHO, if we are about to not support the remote URI, we > should give a error message first. But access local disks > instead of remote disks are definitely wrong here. > > Maybe we also need document this. > > Any thoughts? John Eckersberg is working on implementing this for libguestfs 1.22. Most of the libvirt support has been done already, but there is some more libvirt and libguestfs work. As for reporting an error, it's difficult because libvirt doesn't give a simple way to find out if a URI is "remote" or not (whatever "remote" means). And even if libvirt did, it's not necessarily true that remote URIs wouldn't work, eg. if the user attached a LUN to both the remote and local machine.

Rich.

On Thu, Dec 20, 2012 at 05:30:03PM +0800, Wanlong Gao wrote: > On 12/20/2012 05:08 PM, Richard W.M. Jones wrote: >> On Thu, Dec 20, 2012 at 04:00:10PM +0800, Wanlong Gao wrote: >>> Hi Rich, >>> >>> We just found that the libguestfs can't access the remote URI. >>> When doing guestfs__add_drive_opts(), we always add files from >>> local system, it's related the -c|--connect option. >>> >>> As I know, we are using local kernel to lunch the min-guest, >>> and it's hard to attach remote disks to our local min-guest. >>> >>> Our test team found this problem by using following command, >>> >>> # virt-sysprep -c qemu+ssh://<host>/system -d domname >>> >>> Then, for example the path of remote disk is /work/rhel.img, >>> but we are about to access the /work/rhel.img locally. >>> >>> So, IMHO, if we are about to not support the remote URI, we >>> should give a error message first. But access local disks >>> instead of remote disks are definitely wrong here. >>> >>> Maybe we also need document this. >>> >>> Any thoughts? >> >> John Eckersberg is working on implementing this for libguestfs 1.22. >> Most of the libvirt support has been done already, but there is some >> more libvirt and libguestfs work. >> >> As for reporting an error, it's difficult because libvirt doesn't give >> a simple way to find out if a URI is "remote" or not (whatever >> "remote" means). And even if libvirt did, it's not necessarily true >> that remote URIs wouldn't work, eg. if the user attached a LUN to both >> the remote and local machine. > > So, at this time, we should report a useful message to user but not just > fail without any thing. Right? I don't know how you can report a useful message, since it's not obvious if a libvirt URI is remote. eg. How about the URI "qemu+ssh://foo/session" where the hostname of the local machine is "foo.example.com"? Or the hostname is "bar.example.com" but the local DNS contains a PTR record "foo" -> "bar"?

Rich.

On Thu, Dec 20, 2012 at 05:30:03PM +0800, Wanlong Gao wrote: > On 12/20/2012 05:08 PM, Richard W.M. Jones wrote: > > On Thu, Dec 20, 2012 at 04:00:10PM +0800, Wanlong Gao wrote: > >> Hi Rich, > >> > >> We just found that the libguestfs can't access the remote URI. > >> When doing guestfs__add_drive_opts(), we always add files from > >> local system, it's related the -c|--connect option. > >> > >> As I know, we are using local kernel to lunch the min-guest, > >> and it's hard to attach remote disks to our local min-guest. > >> > >> Our test team found this problem by using following command, > >> > >> # virt-sysprep -c qemu+ssh://<host>/system -d domname > >> > >> Then, for example the path of remote disk is /work/rhel.img, > >> but we are about to access the /work/rhel.img locally. > >> > >> So, IMHO, if we are about to not support the remote URI, we > >> should give a error message first. But access local disks > >> instead of remote disks are definitely wrong here. > >> > >> Maybe we also need document this. > >> > >> Any thoughts? > > > > John Eckersberg is working on implementing this for libguestfs 1.22. > > Most of the libvirt support has been done already, but there is some > > more libvirt and libguestfs work. > > > > As for reporting an error, it's difficult because libvirt doesn't give > > a simple way to find out if a URI is "remote" or not (whatever > > "remote" means). And even if libvirt did, it's not necessarily true > > that remote URIs wouldn't work, eg. if the user attached a LUN to both > > the remote and local machine. > > So, at this time, we should report a useful message to user but not just > fail without any thing. Right? I don't know how you can report a useful message, since it's not obvious if a libvirt URI is remote. eg. How about the URI "qemu+ssh://foo/session" where the hostname of the local machine is "foo.example.com"? Or the hostname is "bar.example.com" but the local DNS contains a PTR record "foo" -> "bar"?

On Thu, Dec 20, 2012 at 06:30:12PM +0800, Wanlong Gao wrote: > On 12/20/2012 05:53 PM, Richard W.M. Jones wrote: > > On Thu, Dec 20, 2012 at 05:30:03PM +0800, Wanlong Gao wrote: > >> On 12/20/2012 05:08 PM, Richard W.M. Jones wrote: > >>> On Thu, Dec 20, 2012 at 04:00:10PM +0800, Wanlong Gao wrote: > >>>> Hi Rich, > >>>> > >>>> We just found that the libguestfs can't access the remote URI. > >>>> When doing guestfs__add_drive_opts(), we always add files from > >>>> local system, it's related the -c|--connect option. > >>>> > >>>> As I know, we are using local kernel to lunch the min-guest, > >>>> and it's hard to attach remote disks to our local min-guest. > >>>> > >>>> Our test team found this problem by using following command, > >>>> > >>>> # virt-sysprep -c qemu+ssh://<host>/system -d domname > >>>> > >>>> Then, for example the path of remote disk is /work/rhel.img, > >>>> but we are about to access the /work/rhel.img locally. > >>>> > >>>> So, IMHO, if we are about to not support the remote URI, we > >>>> should give a error message first. But access local disks > >>>> instead of remote disks are definitely wrong here. > >>>> > >>>> Maybe we also need document this. > >>>> > >>>> Any thoughts? > >>> > >>> John Eckersberg is working on implementing this for libguestfs 1.22. > >>> Most of the libvirt support has been done already, but there is some > >>> more libvirt and libguestfs work. > >>> > >>> As for reporting an error, it's difficult because libvirt doesn't give > >>> a simple way to find out if a URI is "remote" or not (whatever > >>> "remote" means). And even if libvirt did, it's not necessarily true > >>> that remote URIs wouldn't work, eg. if the user attached a LUN to both > >>> the remote and local machine. > >> > >> So, at this time, we should report a useful message to user but not just > >> fail without any thing. Right? > > > > I don't know how you can report a useful message, since it's not > > obvious if a libvirt URI is remote. eg. How about the URI > > "qemu+ssh://foo/session" where the hostname of the local machine is > > "foo.example.com"? Or the hostname is "bar.example.com" but the local > > DNS contains a PTR record "foo" -> "bar"? > > Oops, I don't have a good idea either. > So, as John is doing this work, can you share the working progress and the roadmap > so that we can help doing something? [Adding John to the CC list]

(1) An ugly new libvirt API that runs febootstrap-supermin-helper to create the appliance.

(2) Modify guestfs_add_domain to launch a transient domain using virDomainCreate. (Forget about the live case for the moment).

(3) A new libvirt API to open and forward a virtio-serial channel. This seems generally a useful thing. int virDomainOpenChannel(virStreamPtr, const char *channelid);

(4) libguestfs somehow has to access a virStreamPtr. We can work this one out.