[ADMIN] Getting the initdb parameter values

[Satish Burnwal (sburnwal)]

I have an existing postgres database and I want to know what are the
values of the parameters that were determined during initdb. Is there
any way to know those values ? For example, doc
http://www.postgresql.org/docs/8.1/interactive/runtime-config-resource.h
tml says that the max value of 'shared_buffers' parameter is determined
during initdb. Is there any pg_* table which I look into for such params
?