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Persistent remote X applications with xpra (was: Remote xboard without Desktop Environment)



Hello there,

On Wed, Nov 20, 2013 at 01:33:21PM -0200, Beco wrote:
> [...]
> (3) Now, how can I keep xboard running on lizard, after I turn off fox.

TTBOMK (being former Debian package maintainer of xboard) xboard will
need a DISPLAY to run interactively. ssh -X was already mentioned, but
if the connection gets lost so does any X application running in ssh -X.
screen won't help due to the X requirement. VNC and/or RDP (e.g. via
xrdp) would allow persistent X applications, but both have some overhead
you'd prefer to avoid (and I personally dislike both of them for the
fixed display size of a running session).
So far so bad. xpra might help, though.

Consider the following sample session. fernst is my powerful (ahem...)
workstation, c01n01v01 is a remote virtual server I just had running
(still running Squeeze w/ backports, but still enough to illustrate my
point).

Starting xboard on c01n01v01:

:) fe@fernst:~$ ssh fe@c01n01v01
Linux c01n01v01zfs 2.6.32-26-pve #1 SMP Mon Oct 14 08:22:20 CEST 2013 x86_64

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
fe@c01n01v01zfs:~$ xpra start :8
Entering daemon mode; any further errors will be reported to:
  /usr/users/support/fe/.xpra/c01n01v01zfs-8.log
fe@c01n01v01zfs:~$ DISPLAY=:8 xboard -ncp &
[1] 29158
fe@c01n01v01zfs:~$ ps auxwwkstart_time
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root         1  0.0  0.1   8360   804 ?        Ss   Nov20   0:00 init [2]      
root         2  0.0  0.0      0     0 ?        S    Nov20   0:00 [kthreadd/150]
root         3  0.0  0.0      0     0 ?        S    Nov20   0:00 [khelper/150]
root       340  0.0  0.2  60436  1492 ?        Sl   Nov20   0:00 /usr/sbin/rsyslogd -c4
root       412  0.0  0.1  21160   972 ?        Ss   Nov20   0:00 /usr/sbin/cron
102        704  0.0  0.1  44144  1004 ?        Ss   Nov20   0:00 /usr/sbin/exim4 -bd -q30m
root       728  0.0  1.4  53000  7672 ?        Sl   Nov20   0:14 /usr/bin/python /usr/bin/fail2ban-server -b -s /var/run/fail2ban/fail2ban.sock
root     28523  0.0  0.2  49180  1136 ?        Ss   09:23   0:00 /usr/sbin/sshd
root     29136  0.0  0.6  70464  3288 ?        Ss   09:27   0:00 sshd: fe [priv]  
fe       29138  0.0  0.3  70464  1596 ?        S    09:27   0:00 sshd: fe@pts/0   
fe       29139  0.0  0.3  17712  1908 pts/0    Ss   09:27   0:00 -bash
fe       29148  0.8  4.1 185000 21664 ?        S    09:27   0:00 /usr/bin/python /usr/bin/xpra start :8
fe       29149  2.0  9.7  94236 51160 ?        S    09:27   0:00 Xvfb-for-Xpra-:8 +extension Composite -screen 0 3840x2560x24+32 -nolisten tcp -noreset -auth /usr/users/support/fe/.Xauthority :8
fe       29158  0.6  0.6  45828  3508 pts/0    S    09:27   0:00 xboard -ncp
fe       29161  0.0  0.1  14820  1008 pts/0    R+   09:27   0:00 ps auxwwkstart_time
fe@c01n01v01zfs:~$ logout
Connection to xxx.x.xxx.xx closed.
:) fe@fernst:~$ 

Now connecting to the still running xboard within my xpra session:

:) fe@fernst:~$ xpra attach ssh:fe@c01n01v01:8
Attached (press Control-C to detach)

The xboard window now appears in my regular DE on fernst. I can interact
with it as usual (including resizing it to my liking), and finally
detach (but keep running) as indicated:

^Creceived SIGINT, closing
Connection lost
:) fe@fernst:~$ 

I can reattach again at will. And if not required anymore the xpra
session running on my server can be terminated via

fe@c01n01v01zfs:~$ xpra stop :8

HTH,
Flo


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