How to fix “Failed to connect to Mir” error in python-selenium?

Question

I was about to develop some selenium tests (running with headless firefox), when the following error popped up in the server.log when I was about to acquire the webdriver via this command:

driver = webdriver.Firefox(firefox_profile = profile, log_path = logfile)

Here is the error:

1518520162032   geckodriver::marionette INFO    Starting browser /usr/bin/firefox with args ["-marionette"]
Failed to connect to Mir: Failed to connect to server socket: No such file or directory
Unable to init server: Could not connect: Connection refused
Error: cannot open display: :1137

I do not recall to have changed anything. It just worked before like a hundred times. How to fix that error???

• python 2.7.12
• Firefox: Mozilla Firefox 57.0.3
• geckodriver: 0.19.1
• selenium: 3.8.0

Answer 1

The error says it all :

Failed to connect to Mir: Failed to connect to server socket: No such file or directory
Unable to init server: Could not connect: Connection refused
Error: cannot open display: :1137

This essentially means that the DISPLAY property was not set properly.

Solution

Add the following configuration in your .bashrc :

export DISPLAY=:0

Gnome on Ubuntu 16.04, the correct value is DISPLAY=:1 (not DISPLAY=:0 )

The problem might be due to env_keep variable in /etc/sudoers. So a permanent solution would be to add the following line at the end of /etc/sudoers using gedit or using sudo visudo :

Defaults env_keep+="DISPLAY"

Note : For a detailed discussion see Failed to connect to Mir: Failed to connect to server socket: No such file or directory