Comment 1 for bug 264336

This happens for me too in Intrepid on AMD64, except pgsql attempts to allocate 40MB while the shmax setting is still 32MB.

2008-11-02 00:31:09 GMT FATAL: could not create shared memory segment: Invalid argument
2008-11-02 00:31:09 GMT DETAIL: Failed system call was shmget(key=5432001, size=39288832, 03600).
2008-11-02 00:31:09 GMT HINT: This error usually means that PostgreSQL's request for a shared memory segment exceeded your kernel's SHMMAX parameter. You can either reduce the request size or reconfigure the kernel with larger SHMMAX. To reduce the request size (currently 39288832 bytes), reduce PostgreSQL's shared_buffers parameter (currently 4096) and/or its max_connections parameter (currently 103).
        If the request size is already small, it's possible that it is less than your kernel's SHMMIN parameter, in which case raising the request size or reconfiguring SHMMIN is called for.
        The PostgreSQL documentation contains more information about shared memory configuration.