PostgreSQL のデーモンが起動中に、別のインスタンスを作成することってできないのかな

Test::mysqld みたいなのを作る必要があって、試してみたんだけど、postgres が起動中に initdb を実行すると、

$ /opt/local/lib/postgresql-devel/bin/postgres --version
postgres (PostgreSQL) 8.4devel
$ /opt/local/lib/postgresql-devel/bin/initdb -D data
The files belonging to this database system will be owned by user "kazuho".
This user must also own the server process.

The database cluster will be initialized with locale C.
The default database encoding has accordingly been set to SQL_ASCII.
The default text search configuration will be set to "english".

creating directory data ... ok
creating subdirectories ... ok
selecting default max_connections ... 10
selecting default shared_buffers ... 400kB
creating configuration files ... ok
creating template1 database in data/base/1 ... FATAL:  could not create shared memory segment: Cannot allocate memory
DETAIL:  Failed system call was shmget(key=1, size=1589248, 03600).
HINT:  This error usually means that PostgreSQL's request for a shared memory segment exceeded available memory or swap space. To reduce the request size (currently 1589248 bytes), reduce PostgreSQL's shared_buffers parameter (currently 50) and/or its max_connections parameter (currently 13).
	The PostgreSQL documentation contains more information about shared memory configuration.
child process exited with exit code 1
initdb: removing data directory "data"

みたいなことを言われる。ソースコードをチラ見した共有メモリのキーは、指定されたポート番号によって決まるみたいだけど、PGPORT 環境変数をセットしてもダメっぽい。

ううむ。よくわかんない >_<

18:06追記: http://www.entropy.ch/phpbb2/viewtopic.php?p=2783 で上手く行くようになりました m(__)m