The default values for shared_buffers and max_connections are now 1000

and 100 respectively, if the platform will allow it.  initdb selects
values that are not too large to allow the postmaster to start, and
places these values in the installed postgresql.conf file.  This allows
us to continue to start up out-of-the-box on platforms with small SHMMAX,
while having somewhat-realistic default settings on platforms with
reasonable SHMMAX.  Per recent pghackers discussion.