Xpra failing on localhost

If you know Xpra then you know you can access a "background" X session remotely. It's reasonable to assume that you may also want to access it locally from time to time.

On Ubuntu Precise I was finding that attempting to access the local session failed silently. I have been using:

$ xpra attach -z0 ssh:user@localhost:99

This produces no output. The server log isn't very forthcoming either:

New connection received
Handshake complete; enabling connection
encoding set to rgb24, client supports ['rgb24', 'jpeg', 'png'], server supports ['rgb24', 'jpeg', 'png']
Unhandled error while processing packet from peer
Traceback (most recent call last):
  File "/usr/lib/xpra/xpra/protocol.py", line 338, in _process_packet
    self._process_packet_cb(self, decoded)
  File "/usr/lib/xpra/xpra/server.py", line 1957, in process_packet
    self._packet_handlers[packet_type](self, proto, packet)
  File "/usr/lib/xpra/xpra/server.py", line 1371, in _process_hello
    f = open(mmap_file, "r+b")
IOError: [Errno 13] Permission denied: '/tmp/xpra.QGv7UA.mmap'
connection lost: empty marker in read queue
Connection lost

The clue is in the .mmap. The server needs to be started with the --no-mmap option.

From the man page:

       --no-mmap
              Disables memory mapped pixel data transfer.  By default it is normally  enabled  automatically
              if  the  server  and  the client reside on the same filesystem namespace.

All good!