[CentOS] Multiple program instances or multiple log ins? -- too many Windows assumptions

Tue Dec 27 20:40:07 UTC 2005
Bryan J. Smith <thebs413 at earthlink.net>

Robert Moskowitz <rgm at htt-consult.com> wrote:
> For each of my 'identities' (day job, home business,
> teaching job, etc) to have the mail totally separated.
> Not to have all the mail munged together, particularly
> the in and out boxes!

In Evolution, you must configure this manually.  That's
because Evolution is designed to be an application in the
CORBA 1:1 user:object-framework configuration -- much like
Microsoft Outlook is in the COM+ 1:1 user:object-framework.

You're looking more for an Internet e-mail solution in the
design of Outlook Express, Eudora and Thunderbird.  So
Thunderbird -- out-of-the-box -- is fairly straight-forward.

> Also folder 'foo' can mean one thing at work and another
> for teaching.  Yes, I could name them differently, but I
have
> been doing it this for a lot of years.

Why not use multiple spool directories then?
Or if you want to centralize it on a home server, IMAP
stores?
Then you configure each account to pop to different folders.

Evolution is pretty smart about setting the return address as
it was pop'd.

But in reality, Evolution is _not_ likely the tool you want
to use.  It's really designed for a corporate network with a
1:1 user:object-framework, like MS Outlook or Novell
Groupwise.  You want an Internet e-mail client like MS
Outlook _Express_, Eudora, Thunderbird, etc...

That's why Microsoft makes 2 different products:  Outlook
Express and Outlook.

> So can I run multiple Evolutions?

Yes, like any other multiple X logins, including multiple
CORBA/Bonobo sessions for each user, etc...

How you do that is up to you -- there are at least a
half-dozen ways.

> I suspect I can with multiple workspaces, but that is not
> what I want.

Not the "pager" -- that's completely _different_.  A pager is
just a pager, nothing fancy, Microsoft just doesn't include
the functionality in the GDI in NT5.x (2000/XP) to this point
(maybe in WGF1.x/NT6.0 "Vista" perhaps?).

What you're probably wanting is what (again, I'm using MS
speak here) Citrix calls its ICA client in "seemless windows"
mode.  You launch remote programs from a Citrix server and
they look like local program windows on your local desktop. 
In X-Window, you don't need any special software, or any
separate server for that matter.

Here's a taste (do _not_ run production like this), in a X
terminal, run ...

  $ xhost +
  $ su -  (enter root's password)
  # evolution &

Now you will be prompted with Root's Evolution setup.  If you
run a "ps -eaf |grep -i evo" you will see an instance of
Evolution running for root (as well as your own if you had
Evolution running).  If you do "ps -eaf |grep -i bono" you'll
also see an instance of Bonobo (the CORBA server for GNOME)
running for root, as well as your own.

You can su and run as many programs as you want as whatever
user when you have the local user run "xhost +".  You can
even run programs from _remote_ servers too!  E.g.,

  $ ssh -X bob at remote evolution

Now you will see a new Evolution program and window open, and
it will be the user bob on a remote computer.  In fact,
because the program is running on that remote system, you
will _not_ see the evolution or bonobo instance on the local
system.  But if you ssh over to that system and do a "ps" you
will see them running as bob.  You do _not_ even have to have
a X session on that remote system -- because that system is
displaying the X program on your local X server.

> I am taking this to the gnome support forums (which I
> finally figured out how to find).

Your interest is in the more generic "why UNIX kicks Windows'
ass out-of-the-box in an enterprise" area.  ;->

These concepts are going to seem very foreign -- stuff only
Windows Server and Citrix certified people seem to know about
(at least that is what I tell the people I train) -- all
lock, stock and barrel on that standard $0 Linux CD/DVD.

> I did a search and saw a pointer to 'Fast User Switch
> Applet', but only source no rpm.

Again, you're starting to touch waters that have very, very
different meanings between the UNIX and Windows worlds.

UNIX is inherently _multiuser_ out-of-the-box, and whether
you run a terminal application or an X-Window application,
you can run it remotely, locally, in a window or on its own
desktop.

Citrix had to "hack" and "virtualize" the NT Graphical
Display Interface (GDI) to allow more than 1 user to run
programs at a time.  It's called the "MultiWin" subsystem,
and it's still imperfect compared to UNIX/X's _true_
multiuser.

When you use the "switch user" in NT5.1 (Windows XP) on the
local system, you're merely telling MultiWin to put user X on
the GDI, and virtualize the other user on a virtual GDI in
the background.  Windows Terminal Server (WTS) via the Remote
Desktop Protocol (RDP), as well as Citrix WinFrame/MetaFrame
via the Independent Client Architecture (ICA -- actually has
several acronyms/meanings), allow MultiWin to run completely
virtualized, with _no_ physical GDI, and display on a remote
GDI.

X-Window and today's X-Window version 11 (X11) protocol in
UNIX/Linux systems has done this _inherently_ for 2 decades. 
That's because X11 is just a framework that runs atop of
UNIX's multiuser design, and doesn't care if graphics are
real or virtualized.

Something Gates' decision to _require_ the GDI (i.e., always
have a physical display/KB/mouse) in NT must be worked around
with something like MultiWin.

But you still don't need to worry about this -- just use
Thunderbird instead of Evolution, just like you used Eudora
instead of MS Outlook.


-- 
Bryan J. Smith     Professional, Technical Annoyance                      b.j.smith at ieee.org      http://thebs413.blogspot.com
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*** Speed doesn't kill, difference in speed does ***