Python multiprocessing: Permission denied

Question

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 doesn'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 -ld /dev/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 rw,nosuid,nodev,noexec 0 0 

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