Without -a, multiple runs of xvfb-run will use the same server number. If the first xvfb-run has not freed the resource yet by the time the second xvfb-run is invoked, a conflict will occur, causing an error.
With -a, the second xvfb-run will automatically pick a different server number, thus avoiding the conflict.
Without
-a, multiple runs ofxvfb-runwill use the same server number. If the firstxvfb-runhas not freed the resource yet by the time the secondxvfb-runis invoked, a conflict will occur, causing an error.With
-a, the secondxvfb-runwill automatically pick a different server number, thus avoiding the conflict.CC: @samth