Si je met une valeur supérieur 5GB pour shared_buffers:

[....] Restarting PostgreSQL 9.1 database server: main[....] The PostgreSQL server failed to start. Please check the log output: 2014-09-17 15:08:06 CEST FATAL: could not create shared memory segment: No space left on device 2014-09-17 15:08:06 CEST DETAIL: Failed system call was shmget(key=5432001, size=10990821376, 03600). 2014-09-17 15:08:06 CEST HINT: This error does *not* mean that you have run out of disk space. It occurs either if all available shared memory IDs have been taken, in which case you need to raise the SHMMNI parameter in your kernel, or because the system's overall limit for shared memory has been reached. If you cannot increase the shared memory limit, reduce PostgreSQL's shared memory request (currently 10990821376 bytes), perhaps by reducing shared_buffers or max_connecti[FAILThe PostgreSQL documentation contains more information about shared memory configuration. ... failed!
failed!