Why do I get Permission denied for pid file when launching roscore

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Hi,

I installed ros on a Xenial box, initialized the environment but get the following when I try to start roscore:

osboxes@osboxes:~$ roscore  Traceback (most recent call last):   File "/opt/ros/kinetic/lib/python2.7/dist-packages/roslaunch/__init__.py", line 257, in main
    write_pid_file(options.pid_fn, options.core, options.port)   File "/opt/ros/kinetic/lib/python2.7/dist-packages/roslaunch/__init__.py", line 110, in write_pid_file
    with open(pid_fn, "w") as f: IOError: [Errno 13] Permission denied: '/home/osboxes/.ros/roscore-11311.pid'

even though:

osboxes@osboxes:~$ ls -l /home/osboxes/.ros/roscore-11311.pid
-rw-r--r-- 1 root root 5 Feb 16 20:28 /home/osboxes/.ros/roscore-11311.pid

the user has r&w access to the file, what's wrong, am I missing something?