[CentOS] Multiple program instances or multiple log ins?

[Bryan J. Smith]

Robert Moskowitz <rgm at htt-consult.com> wrote:
> This all comes out of figuring out how I might run
> Evolution like I run Eudora.
> I see where Evolution places its data in a hidden
> directory: ~/.evolution
> Now why it is felt necessary to put all of this stuff in
> hidden directories is beyond me.

User settings, index files, filters, etc...

> So it would seem that Evolution is treating each useid as a
> personality for the logged in user.

Correct.  This is because Evolution taps into the CORBA
system (Bonobo) to exchange objects with other GNOME
applications.  That is tied to the GNOME Session, it's Bonobo
instance, etc... which is the logged in user on the current X
session (default of ":0.0" for a local X Server).

> Given the way Evolution organizes its data, I could create
> some more Linux users, and either:
> Give my main user file permissions to them and somehow run
> copies of Evolution using those /home/user directories.

NFS?  More on that below.

> Anyone know how to do that?

I'm confused here.  Why do you need more than 1 instance of
Evolution running on a system?

I can understand more than 1 system accessing the same user
home directory.  In that case, GNOME 2.x, it's Bonobo and
Evolution 1.4+ all respect the same user home directory
mounted via NFS (with NFS locking) from multiple systems with
multiple instances.  Although I do highly recommend you use
IMAP folders instead of the default mbox mail folders, or at
least maildir for the local mail folder formats.

Likewise, if you have multiple users accessing the same
mailboxen from different user accounts (and resulting GNOME
logins and Evolution sessions), then use IMAP to store those
folders as well.  In such cases you're talking more
login/server-level details that Evolution -- just like if you
had an Exchange/Outlook setup as well.

As I've stated before on this list and others, Evolution is
not designed as an Internet e-mail client, it is an
enterprise collaboration client.  It does not compare well
with Eudora, Thunderbird, etc...  If you long for the more
"direct/straight-forward" features of Eudora, check out
Thunderbird.  If you are looking for the 1:1 single sign-on
(SSO), desktop environment integrated collaboration client,
then the GNOME-Evolution is the solution you are looking for.

> Or do I somehow have to have multiple simultaneous logins?

I don't see why.  What are you trying to do _exactly_?!

I think you're coming to conclusions based on what you think
you need, when you're not providing what you really need to
do -- that's something we can advise you best on.

> And switch between them?  I know there is a way to have 4
> desktops....

You're thinking of the "pager" functionality -- "desktops"
and/or "viewports" where the terminology varies based on X
framework.  Despite not shipping something in stock Windows,
you _can_ get "pager" like functionality for Windows as well.

A "pager" is still part of the same root desktop -- again,
:0.0 for a system that has a local X Server that comes up at
boot.

You _can_ run multiple X sessions allowing multiple logins. 
In fact, you can use XDM (e.g., :1.0 on Ctrl-Alt-F8, :2.0 on
Ctrl-Alt-F9, etc...), XDMCP (local or even remote "Windows
Terminal Server-like"** access), Xnest (avoids the need for
and security issues of XDMCP) and/or Xvnc (another option
that uses remote framebuffer, instead of X11, so non-X
clients can access the desktop -- kinda like Symantec
pcAnywhere**) to setup physical, nested, virtual, etc... X
sessions on a single system -- each with their own logins. 
But, again, I don't think that's what you want to be doing.

BTW, you don't even need to go that far.  You can give
another user X Authority (xauth) to access your _single_ :0.0
X session, then switch user (su) and display programs on the
same desktop.  If you really don't care about security, you
can just run "xhost +" and that allows _any_ user to launch a
program to your desktop (I do _not_ recommend this).  This is
yet another option, kinda like Citrix ICA "seemless
windows-like"**.

I use xauth to authorize select users to launch 2-3 different
Firefox (one for Internet, one for Intranet, one for secure
web administration, etc...), Thunderbird and even the
occassional, multiple Evolution programs running as
_different_ users on the _same_, _single_ :0.0 X desktop. 
The respective GNOME framework, including Bonobo, for each
respective user -- completely separate from one another
_except_ they are displayed on the same :0.0 X desktop**.

[ **NOTE:  These comparisons to Microsoft WTS/RDP and Citrix
ICA are rather insults to X-Window, which pre-dates both. 
But I only make them to relate to those Windows familiar --
Xvnc is like Symantec pcAnywhere, only you can have dozens of
simultaneously sessions, XDMCP/Xnest is kinda like WTS/RDP
"full desktop" and normal Xauth/X11 operation is kinda like
ICA in "seemless windows" where you still have your single
desktop. ]


-- 
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 ***