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RE: XWin and multiple users


On Tue, 25 May 2004, Kris Thielemans wrote:

> > Just for the record: another solution is to make /tmp a user mount, and
> > have it in a different location for each user.  That has other
> > connotations, presumably, but I thought I'd mention it here for
> > completeness.
>
> I seem to remember that user mounts are ignored by services.  As sshd
> (usually?) runs as a service, this might mean that sshd wouldn't run
> properly anymore. ok,maybe one could have a system mount for /tmp AND
> user mounts. A bit scary though.
>
> Kris

User mounts are most definitely *NOT* ignored by services -- as long as
they are for the appropriate user.  Services run as a *user* on your
machine called SYSTEM (note the case; a.k.a.  LocalSystem), and if that
*user* has user mounts, they work just like for any other user.  User
mounts for the SYSTEM user are not the same as system mounts.  Some of the
"connotations" that I mentioned above are that a) it's usually hard to set
up and later detect SYSTEM mounts, and b) if you, at some point, decide to
change the root mount of Cygwin, services may indeed not run properly
anymore (because they will have a user mount that overrides the system one
*and* points to a now non-existent directory).

Also, as you pointed out, it *is* possible to have a system mount for /tmp
and a few user mounts for /tmp (one for each user).  The user ones will
override the system ones when they're present.  For a user with no user
mounts (e.g., SYSTEM), a system mount will be used.

As I said, this is here mostly for completeness.  You're absolutely right
that it's scary -- it should be (at least for essential paths like
"/usr/bin", etc).  It is, in general, rather dangerous to have both user
and system mounts for the same paths, as they can run out of sync very
easily.  So use this setup at your own risk, and only if you know what
you're doing (or had it explained to you in detail).  However, it should
work just fine for /tmp, unless you have some application that relies on
*sharing* data between users through /tmp (anyone know of any?).
	Igor
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