I often log into a remote SSH terminal to use an
ipython shell. In doing so, it is necessary for me look at figures invoked by
matplotlib as I am exploring and analysing data. For this, I have comfortably been using a combination of
xpra. However, I recently hesitantly upgraded my Ubuntu distribution from 14.04 Trusty Tahr to 16.04 Xenial Xerus. And with all upgrades, I expected minor breakages. Little did I realise that it would break
xpra and interrupt my workflow sending me down a rabbit hole internet trawling for solutions. Turns out it is a known issue on on launchpad but the discussion has not been active for a while and the provided solutions were incomprehensible to a lay user. It appears that simply updating
xpra to the latest version resolves the issue.
Log into the report server:
ssh -Y username@remote
On the remote server, update to the latest stable release of
xpra which at the time of writing this was
2.0-r15319-1. The update instructions which were not so obvious to find are as follows:
# Administrator privileges sudo su - # Import the packager's key: apt-get install curl curl http://winswitch.org/gpg.asc | apt-key add - # Xenial Xerus (16.04) echo "deb http://winswitch.org/ xenial main" > /etc/apt/sources.list.d/winswitch.list; apt-get install software-properties-common >& /dev/null; add-apt-repository universe >& /dev/null; apt-get update; apt-get install winswitch
Now start an
xpra server and attach to the session inside a
xpra start :10 xpra attach :10
Ctrl+a, d to detach from the screen session. Now run the following on a separate
screen session which should launch a beautiful empty plot on your client.
DISPLAY=:10 ipython --pylab -c 'plot()'
To replicate the problem on a vanilla installation of Ubuntu 16.04 with the default installation of
0.15.8+dfsg-1 amd64 at the time of writing this blog:
ssh -Y username@remote xpra start :10
I tried to create a
plot() as usual in
ipython shell with
pylab module using the default
DISPLAY=:10 ipython --pylab -c 'plot()'
Which generated the following error:
: cannot connect to X server :10
I inspected the content of my log by running
/usr/lib/xorg/Xorg.wrap: Only console users are allowed to run the X server 2017-03-15 15:03:37,413 2017-03-15 15:03:37,413 Xvfb command has terminated! xpra cannot continue 2017-03-15 15:03:37,413
I found these discussions to change
allowed_users=anybody by running
sudo dpkg-reconfigure xserver-xorg-legacy for a GUI interface or alternatively by running the following
sed command on
sudo sed -i 's/allowed_users=console/allowed_users=anybody/' /etc/X11/Xwrapper.config
Now when I ran
xpra start :10, noticed that my
plot() function still was not working. I inspected the log using
cat ~/.xpra/:10.log again and saw the following:
~/.xpra/IT050339-10 is not responding, waiting for it to timeout before clearing it.(EE) Fatal server error: (EE) The '-logfile' option cannot be used with elevated privileges. (EE) (EE) Please consult the The X.Org Foundation support at http://wiki.x.org for help. (EE) .... 2017-03-15 13:15:38,963 2017-03-15 13:15:38,963 Xvfb command has terminated! xpra cannot continue 2017-03-15 13:15:38,963 2017-03-15 13:15:38,963 removing socket /home/bk12369/.xpra/IT050339-10
I thought I would try launching
xpra as a superuser so I ran
sudo xpra start :10. When I inspected the log this time using
cat ~/.xpra/:10.log, this is what I saw:
X.Org X Server 1.18.4 Release Date: 2016-07-19 X Protocol Version 11, Revision 0 Build Operating System: Linux 4.4.0-45-generic x86_64 Ubuntu Current Operating System: Linux IT050339 4.4.0-66-generic #87-Ubuntu SMP Fri Mar 3 15:29:05 UTC 2017 x86_64 Kernel command line: BOOT_IMAGE=/boot/vmlinuz-4.4.0-66-generic root=UUID=51981f04-c04d-4b55-a28d-31f545fa32b7 ro quiet splash Build Date: 02 November 2016 10:06:10PM xorg-server 2:1.18.4-0ubuntu0.2 (For technical support please see http://www.ubuntu.com/support) Current version of pixman: 0.33.6 Before reporting problems, check http://wiki.x.org to make sure that you have the latest version. Markers: (--) probed, (**) from config file, (==) default setting, (++) from command line, (!!) notice, (II) informational, (WW) warning, (EE) error, (NI) not implemented, (??) unknown. (++) Log file: "/home/bk12369/.xpra/Xorg.:10.log", Time: Wed Mar 15 15:30:37 2017 (++) Using config file: "/etc/xpra/xorg.conf" (==) Using system config directory "/usr/share/X11/xorg.conf.d"
This was what I initially expected to see but when I ran
DISPLAY=:10 ipython --pylab -c 'plot(), it still refused to work by producing the following error:
No protocol specified : cannot connect to X server :10
Note that this is slightly different to earlier since it recognises that there is an open port but still struggling to connect. Next, I found that changing the permission for
~/.Xauthority enabled me to query all the current sessions as follows:
sudo chown $USER:$USER ~/.Xauthority xauth list | grep `uname -n`
IT050339/unix:10 MIT-MAGIC-COOKIE-1 e65eee56adec473c9a04c74e2089f8b7
This allowed me to run
DISPLAY=:10 ipython --pylab -c 'plot() without any errors. However, I was still unable to attach to the session using
xpra attach :10.
This is when I decided to update
xpra to the latest branch as per the instructions provided in TL;DR which took a great difficulty to find which resolved everything.
Persevere and keep trying new things.