[Dev] How to share files with Cynara

Schaufler, Casey casey.schaufler at intel.com
Mon May 5 15:49:52 GMT 2014

> -----Original Message-----
> From: Jussi Laako [mailto:jussi.laako at linux.intel.com]
> Sent: Monday, May 05, 2014 1:44 AM
> To: Schaufler, Casey
> Cc: dev at lists.tizen.org
> Subject: Re: [Dev] How to share files with Cynara
> On 2.5.2014 1:20, Schaufler, Casey wrote:
> >> + data shared between group of users
> >
> > Sorry, but I have never seen this as a requirement.
> I don't know if it is written down somewhere, but it is very common type of
> sharing case.

On a general purpose, multiuser computer of course it is.

> At bare minimum, to me, it would make sense to differentiate at least
> between occasional "guest" users and normal "privileged" users of the
> system who have real user account.

Sure, but that does not make the general case interesting.

> >> So we need at leas one overall "Public" folder in the system.
> >
> > Which is a *direct* violation of the application isolation requirement.
> If you can for example download PDF and open it in a PDF reader application
> you already violate the application isolation. This is no different. When I
> download a PDF document on Android, it asks me if I want to open it in
> Acrobat Reader or some other reader capable of handling PDFs.

Tizen isn't Android. If Android set the battery on fire every first if June,
would you want Tizen to do it, too?

> It is very common use case that you would like to share a photo or similar file
> with other users of the system. Having to upload it to cloud service like
> OneDrive or DropBox to allow sharing it is just additional annoyance for the
> end user. And from "application isolation"
> point of view there's no difference. It's the same file, regardless if you load it
> from local storage or from a web URL.

OK, but that says nothing about "groups of users".

> >> You could create
> >> a group called "Family" with gumd and assign family members to it and
> >> then share for example family vacation photos in that folder.
> >
> > You could, but what requirement are you addressing?
> Common sense requirement... ;)

(Casey spews coffee through his nose)

Sorry, but if you get to invoke "common sense" so do I,
and I *know* that I don't get to.

> We don't have any detailed requirements for multi-user while multi-user
> support in itself brings up number of new use cases and likely necessary
> requirements such as ability to share files between multiple users of the
> same system.

OK, let's look at other multiuser mobile devices. They are implementing
BYOD, and explicitly prohibit sharing. Let's consider the airplane seatback,
where you want to have multi-user games, but the "user" is ethereal.
The car? OK, who's going to administer groups?

> I know only about 20 high level "hands waving" requirements for multi-user
> and that's all.
> >> This is why I'm advocating "group home" folders, for example
> >> /home/groups/Family with root:Family 770 permissions.
> >
> > This *is not* a general purpose Linux system. Unless there is a
> > requirement that we have a mechanism to do this there is no reason to
> > worry about it, and good reasons not to.
> I'm just trying to think about usability from normal users' point of view.

Right. Usability is a good thing. Unfortunately, what makes it easy to
share photos makes it easy to share viruses.

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