RFC: baseline requirements for Ubuntu rootfs: xattrs and fscaps

[Steve Langasek]

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?

-- 
Steve Langasek                   Give me a lever long enough and a Free OS
Debian Developer                   to set it on, and I can move the world.
Ubuntu Developer                                   https://www.debian.org/
slangasek at ubuntu.com                                     vorlon at debian.org
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