Re: [Libguestfs] Fwd: Re: VirtFS Query

On Thu, 29 Sep 2011 17:12:22 +0100, "Richard W.M. Jones" <rjones(a)redhat.com&gt; wrote: > On Thu, Sep 29, 2011 at 09:19:03PM +0530, Harsh Bora wrote: > > Richard, FYI. > > > > On Wed, 28 Sep 2011 17:05:42 +0530, Harsh Bora > > <harsh(a)linux.vnet.ibm.com&gt; wrote: > > >Hi Aneesh, > > > > > >Richard asked me if we have any plans to provide a solution for this use > > >case: > > > > > >https://www.redhat.com/archives/libguestfs/2011-September/msg00089.html > > > > > >IIUC, VirtFS as a rootfs is targeted towards this requirement only, > > >right? Any inputs ? > > > > > > > The right way to do this is to use a export path /guest and bind mount > > needed directories within. VirtFS just export /guest and everything > > works out easily. I already have autotest driving virtFS as root. So > > that works easily > > That's not going to work for us. > > Firstly bind mounting requires root, which is no good for libguestfs. > Another alternative suggested by pekka for tools/kvm (native linux kvm) is to create a directory layout as below in /guest1-export/ bin -> /host/bin sbin -> /host/sbin usr -> /host/usr lib -> /host/lib etc proc var host and qemu starts with two export path /guest1-export as root and / of the common image (or host) as /host on guest. Now 9p resolves symbolic links in the guest. So which ever directory that need to be shared with host can have a symlink and everything works

> Secondly there are no directories that we could bind mount. We really > need the flexibility outlined in that email. Just two examples of > this (there are more): > > - /usr/sbin in the appliance is not the same as /usr/sbin on the > host. The appliance version should contain a subset of the host > directory, plus at least one extra binary (/usr/sbin/guestfsd). > > - Because /etc files on the host can be arbitrarily modified, we need > to construct our own /etc directory, with files from the host and > files that we supply. > > What's may help here is some sort of plugin or passthrough mechanism > letting us add our own 9p server/plugin without pushing all the > complexity we need into qemu sources. > > More here: > http://libguestfs.org/febootstrap.8.html#supermin_appliances There is some level of plugability with VirtFS server already. You can look at virtio-9p-local.c, virtio-9p-handle.c and virtio-9p-synth.c in the example. git://repo.or.cz/qemu/v9fs.git