[winswitch] Xpra "can't open display" error

[Antoine Martin]

On 30/04/18 01:59, pxd--- via shifter-users wrote:
> Hi,
> Using Xpra 2.3-r19058 from the Xpra Debian buster repo (on client and server), I can't get the display to get sent over ssh from a headless VM to the VM's host machine.
> 
> From the client machine, if I run:
> xpra start ssh:hostname:102 --start-via-proxy=no
> 
> I get:
> xpra initialization error:
>  failed to identify the new server display
> Error: failed to receive anything, not an xpra server?
>   could also be the wrong protocol, username, password, or port
> Connection lost
That's usually an ssh connection problem, or maybe the server took too
long to start.
Try starting the server in advance from a server shell then run "attach"
from the client.

> But `xpra list` on the host machine shows that display :102 was successfully started and live. (If I do the above without `--start-via-proxy=no`, I get the same errors and can see  the xpra command running with `ps aux`, but I can't connect to it, there are no xpra sessions found with `xpra list` and I have to manually kill the xpra process.) 
> 
> I can attach to the session without any client side errors with `xpra attach ssh:hostname:102`, but can't get any windows sent over the connection.
> 
> On the server, if I run `DISPLAY=:102 xterm`,
This should be avoided. If possible, always use "--start=xterm" instead,
this will use the correct environment settings to run the command.

> I get "No protocol specified" and "xterm: Xt error: Can't open display: :102". Firefox similarly gives me "No protocol specified / Unable to init server: Could not connect: Connection refused / Error: cannot open display: :102".
Details can be found in:
http://xpra.org/trac/ticket/1776

xpra 2.3 will not use "private XAUTHORITY files" by default to avoid
this sort of confusion, but this behaviour can be changed using the
XPRA_PRIVATE_XAUTH environment variable.

> I can start xterm through an ssh session with X-forwarding, so X is somehow working.
> 
> The full xpra start and Xorg commands as shown in ps aux are:
> /usr/bin/python2 /usr/bin/xpra start :102 --start-via-proxy=no --env=XPRA_PROXY_START_UUID=(some long uuid) --daemon=yes --systemd-run=no
> /usr/lib/bin/xorg/Xorg-for-Xpra-:102 -noreset -novtswitch -nolisten tcp +extension GLX +extension XRANDR +extension RENDER -auth /run/user/1000/xpra/Xauthority-102 -logfile /run/user/1000/xpra/Xorg.:102.log -configdir /run/user/1000/xpra/xorg.conf.d/9075 -config /etc/xpra/xorg.conf -depth 24 :102
> 
> Errors in Xorg.:102.log are:
> (EE) Unable to open config directory: "/run/user/1000/xpra/xorg.conf.d/9075"
> (EE) systemd-logind: failed to take device /dev/dri/card0: Operation not permitted
> (EE) AIGLX: reverting to software rendering
> and a bunch of (EE) Failed to load module something (module does not exist, 0), where "something" is mouse, kbd, libinput
All of those can be safely ignored.

> Errors in :102.log are:
> /bin/sh: 1: dbus-launch: not found
> dbus-launch failed to start using command 'dbus-launch --close-stderr':
>  exit code is 127
Not sure why dbus-launch would fail here, is it installed correctly?
> (but later there is the message "D-Bus notification forwarding is available")
> And the log ends with "xpra is ready / printer forwarding enabled.... / 3.9GB of system memory"
> 
> The VM running the Xpra server is a fresh Debian Buster install (without any graphical desktop environment) where I just `apt-get install xpra`ed. Interestingly, on a fresh Debian Buster + Gnome 3 install, I get a similar issue with `xpra start` apparently failing but still starting the display and letting me connect with `xpra attach`. On that VM, I can get a window sent over if I add the flags ` --start-via-proxy=no --xvfb="/usr/bin/Xwayland -rootless -noreset` to the start command to use Gnome's Xwayland X server.
Please file a ticket. Debian Buster is not a high priority at the moment
as it is still pretty far from its release date, but this should
eventually be fixed.

Cheers
Antoine

> 
> Any ideas of where to poke to get more information on what's going wrong?
> 
> Thanks!
> 
> Persimmon
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