[Box-Admins] understanding remote image viewing options

Chris Muller asqueaker at gmail.com
Mon Nov 11 16:19:49 UTC 2013

Levente, I'm glad you posted about xpra, because I've been meaning to
try it out as well as Squeak's RFB.

I would like to ask you (and others here of course!) about options for
remote image operation, and try to understand the differences between
them.  By my understanding, we have 1) VNC, 2) Squeak RFB and 3) xpra.

(VNC desktop) Sharing entire desktops on my LAN is handy for accessing
multiple running images on another machine all at once.  The downside
is that it's single-user, since anyone else trying to use the desktop
will be disrupted.

(VNC display :1) Sharing an alternate display by starting xtightvnc on
the server, starting Squeak vm with the -display :1 argument, one can
then use remote viewing tools like Remmina to reconnect to that
running Squeak image.

(xpra) This is for sharing a single program at a time.  You can start
an image on a particular display.  This seems similar to above except
it can run across ssh rather than having to share a VNC password..?
One thing I was wondering was whether the Squeak vm could be started
with the -display arg like above or only that strange way you said:
$DISPLAY=:100 squeak -vm-sound-null squeaksource.image..?

(Squeak RFB) From Ian, my understanding is this uses the image itself
to send its graphics over the network for remote op.  Might slow down
the image but the advantage here could be if you're on a machine on
which you cannot install and/or run remote viewing software..?

I'm no expert, thanks for any comments and/or clarifications.

On Mon, Nov 11, 2013 at 1:59 AM, Levente Uzonyi <leves at elte.hu> wrote:
> On Sun, 10 Nov 2013, David T. Lewis wrote:
>> For information - no action required:
>> Our squeaksource.com service is running with no apparent problems, but
>> there is a possibility of problems arising in the next day, so I am
>> sending this for information.
>> I checked our squeaksource.com image on box3 via VNC about an hour ago,
>> and noticed an error notifier related to startup processing following
>> an image save. The error was related to port 8888 already in use. I
>> closed the notifier, then found that http://squeaksource.com was no
>> longer active.  I made a backup copy of the most recently saved disk
>> image (in a BACKUPS subdirectory), then saved the image and restarted
>> it.
>> Squeaksource.com is running normally, but VNC access is no longer
>> working. This means that something failed in the startup processing,
>> and this may lead to problems later on. It also means that it is
>> hard to debug, because I no longer have VNC access.
>> I cannot do anything further tonight, but will follow up tomorrow
>> to correct the problem.
> It would be worth installing xpra[1][2], and starting the image with it.
> IIRC the box has debian installed on it, so the following steps should work:
> On the server:
> Installation:
> $ sudo apt-get install xpra
> Start xpra on display #100:
> $ xpra start :100
> Start the VM (this might have to be different on the server):
> $ DISPLAY=:100 squeak -vm-sound-null squeaksource.image
> On your machine:
> Once you have xpra installed, you can attach to squeak running on the server
> via ssh:
> $ xpra attach --encoding=jpeg --auto-refresh-delay=0.1 ssh:box3:100
> Here box3 is the label defined in the ssh config file, which can usually be
> found in $HOME/.ssh/config
> If you don't have such entry or file yet, then the following will do the
> trick:
> Host box3
>      hostname box3.squeak.org
>      user <your_username>
>      compression yes
>      port 22
> You might want to use a different value for the --auto-refresh-delay
> parameter.
> To detach from the image - but keep it running on the server - simply stop
> the xpra on your machine with Ctrl-C.
> Levente
> [1] http://xpra.org/
> [2] https://help.ubuntu.com/community/Xpra
>> Dave

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