Python multiprocessing: Permission denied

Question

Hi guys, I'm getting an error when trying to execute python program that uses multiprocessing package:

  File "/usr/local/lib/python2.6/multiprocessing/__init__.py", line 178, in RLock
    return RLock()
  File "/usr/local/lib/python2.6/multiprocessing/synchronize.py", line 142, in __init__
    SemLock.__init__(self, RECURSIVE_MUTEX, 1, 1)
  File "/usr/local/lib/python2.6/multiprocessing/synchronize.py", line 49, in __init__
    sl = self._semlock = _multiprocessing.SemLock(kind, value, maxvalue)
OSError: [Errno 13] Permission denied

It looks like the user don't have permission to access shared memory. When executing with root privileges it works fine.

Is there any solution to run it as normal user(not root)?

Python version 2.6.2 , OS is Linux 2.6.18 (CentOS release 5.4) and it's VPS machine.

Answer 1

For POSIX semaphores to work, the users need r/w access to shared memory (/dev/shm).

Check the permissions to /dev/shm. On my laptop (Ubuntu) it looks like this:

$ ls -l /dev/ | grep shm
drwxrwxrwt 2 root root          40 2010-01-05 20:34 shm

To permanently set the correct permissions (even after a reboot), add the following to your /etc/fstab:

none /dev/shm tmpfs defaults 0 0

Haven't tried this, just copied from a forum post.