RFC: baseline requirements for Ubuntu rootfs: xattrs and fscaps

[Jamie Strandboge]

On Mon, 2018-08-06 at 14:53 -0700, Steve Langasek wrote:
> Hi John,
> 
> On Mon, Aug 06, 2018 at 10:09:53PM +0100, John Lenton wrote:
> > On Mon, 6 Aug 2018 at 21:16, Steve Langasek <steve.langasek at ubuntu.
> > com> wrote:
> > > I think it's exceedingly unlikely that anyone is going to unpack,
> > > and
> > > subsequently boot, an Ubuntu root tarball on a filesystem that
> > > doesn't
> > > support xattrs.  All the filesystems that Ubuntu supports out of
> > > the box as
> > > rootfs (in terms of installers, and filesystem tools
> > > preinstalled) support
> > > xattrs.
> > while this is strictly true, 'snap pack' and 'snapcraft pack'
> > currently disable xattrs, and the store will not approve snaps that
> > are built with xattrs.
> 
> Thanks, that's a useful data point.  Do you think it is a practical
> concern
> for snaps if an Ubuntu rootfs uses fscaps?  Is this an argument
> against
> allowing fscaps in Ubuntu, or should it just be a matter for
> snapcraft to
> warn/error about on creation, guiding users to using setuid instead?
> 
> As a worked example: the core snap does ship /bin/ping, which is
> currently
> setuid-root in Ubuntu but would move to fscaps in this
> proposal.  (The core
> snap does not include mtr-tiny.)  What do you believe is the correct
> outcome
> here for /bin/ping in a future ubuntu core 20 snap?

App snaps are currently expected to be generated with --no-xattrs and I
continue to believe this is the correct choice for the time being.

os/base snaps need not be expected to be built this way and we while
might have some light review tools updates for this, in principle it is
not a problem for os/base snaps.

-- 
Jamie Strandboge             | http://www.canonical.com
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