Re: [PATCH] test: fix 'make assets' failure as root

[Yumei Huang <yuhuang@redhat.com>]

On Thu, Sep 25, 2025 at 6:54 PM Stefano Brivio <sbrivio@redhat.com> wrote:
>
> On Thu, 25 Sep 2025 11:27:49 +0100
> "Richard W.M. Jones" <rjones@redhat.com> wrote:
>
> > On Thu, Sep 25, 2025 at 11:40:25AM +0200, Stefano Brivio wrote:
> > > On Thu, 25 Sep 2025 09:53:06 +0100
> > > "Richard W.M. Jones" <rjones@redhat.com> wrote:
> > >
> > > > On Thu, Sep 25, 2025 at 01:43:06PM +0800, Yumei Huang wrote:
> > > > > Running `make assets` under `test` as root fails with a "Permission denied"
> > > > > error when `prepare-distro-img.sh` invokes `virt-edit` and `guestfish`. This
> > > > > is due to a known bug in libvirt.
> > > > >
> > > > > Work around the issue by switching to the direct backend.
> > > > >
> > > > > Signed-off-by: Yumei Huang <yuhuang@redhat.com>
> > > > > ---
> > > > >  test/prepare-distro-img.sh | 2 ++
> > > > >  1 file changed, 2 insertions(+)
> > > > >
> > > > > diff --git a/test/prepare-distro-img.sh b/test/prepare-distro-img.sh
> > > > > index 0d967c9..423eea7 100755
> > > > > --- a/test/prepare-distro-img.sh
> > > > > +++ b/test/prepare-distro-img.sh
> > > > > @@ -3,6 +3,8 @@
> > > > >  IMG="$1"
> > > > >  PASST_FILES="$(echo ../*.c ../*.h ../*.sh ../*.1 ../Makefile ../README.md)"
> > > > >
> > > > > +export LIBGUESTFS_BACKEND=direct
> > > >
> > > > Please add a comment that this is only added as a temporary hack until
> > > > we can get a proper fix (in libguestfs possibly, see Dan's earlier
> > > > email).
> > >
> > > On the other hand, regardless of that fix, I would be happy to be run
> > > this on single-user Alpine L1 guests, eventually, where libguestfs
> > > doesn't depend on libvirt (see my caveat 2.), and I usually reserve
> > > very little disk space for those.
> >
> > The upstream default is backend 'direct'.  In Fedora & RHEL we
> > override this with 'libvirt':
> >
> > https://src.fedoraproject.org/rpms/libguestfs/blob/rawhide/f/libguestfs.spec#_714
>
> Ah, sorry, I had no idea!
>
> > I don't know what Alpine does, but likely it leaves it at the default.
> > (You can try: `guestfish get-backend`)
>
> Yes, this is guestfs-tools and libguestfs 1.56.1-r0 on Alpine:
>
>   # guestfish get-backend
>   direct
>
> Same on any modern Debian, openSUSE, Ubuntu.
>
> > > If you don't have compelling reasons (like you're dropping
> > > LIBGUESTFS_BACKEND=direct in two weeks), I would simply keep this as
> > > long as it works. The day you drop that, we'll drop this too.
> >
> > We're not dropping the environment variable / feature ever.  The
> > problem is that this was cargo-culted into a lot of code over the
> > years, and it does reduce the security of libguestfs on RHEL.  We're
> > having an (ongoing) battle to remove this cargo-culting from CNV right
> > now.  I'm just not keen to add this line in new places, without at
> > least a comment saying this is a temporary hack, and not generally
> > recommended.
>
> Oh, I see, that makes sense.
>
> But then, Yumei, we should also add to that comment (sorry, this is
> becoming much more complicated than I thought...) that the workaround
> is for Fedora and related distributions.

I will update in v2. Thank you all for the comments.
>
> --
> Stefao
>


-- 
Thanks,

Yumei Huang