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I successfully created a privileged lxc archlinux container on an archlinux host with lxc. I set up a static ip via dnsmasq and ssh into it and I use xauth to forward X11. I then call programs like mupdf or plot functions from programming languages such as R or Matlab. While this all works fine I constantly see error messages printed to the console when I open a *.pdf file with mupdf:

     ximage: disabling shared memory extension: BadAccess (attempt to access private resource denied)

Two short questions about this:

  1. What exactly does this error message mean?
  2. How can this error be solved (or is it safe to ignore)?
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Shared memory is a mechanism to exchange rendered image without having to use sockets, the protocol works something like this: X client create the shared buffer, X client tell the server that's where you will find the images i create, the server "attach" itself to the shared memory and refresh whenever there is an update, this mechanism is 10x of socket transfer, but slower than zero-copy rendering. if you wish you can disable this mechanism by settings these environment variables:


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