Wednesday, 15 August 2018

Re: RFC: baseline requirements for Ubuntu rootfs: xattrs and fscaps

On Mon, Aug 6, 2018 at 5:53 PM 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 <> 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?

The upcoming Fedora base snap is likely to require maintaining xattrs,
since we heavily use fscaps, among many other things. So this
requirement will likely change.

真実はいつも一つ!/ Always, there's only one truth!

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