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\         


        

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.

Answer 2

In my OVH VPS Classic, this error was caused by a loop in /dev/shm and /run/shm. Both were symlinks linking to each other. So as root here is what I did:

# rm /dev/shm
# mkdir /dev/shm
# chmod 777 /dev/shm
# nano /etc/fstab

Then I modified the shm line from:

none /dev/shm tmpfs rw 0 0

To:

none /dev/shm tmpfs rw,nosuid,nodev,noexec 0 0

Restarted the server... And that fixed the problem! Alternatively you can mount shm manually:

# mount /dev/shm

Hope this helps :-)

Answer 3

One simple solution without rebooting is

sudo chmod 777 /dev/shm

That solved my problem.