How can I start PostgreSQL server on Mac OS X?

Final update:

I had forgotten to run the initdb command.

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By running this command

ps auxwww | grep postgres

I see that postgres is not running

> ps auxwww | grep postgres
remcat          1789   0.0  0.0  2434892    480 s000  R+   11:28PM   0:00.00 grep postgres

This raises the question:

How do I start the PostgreSQL server?

Update:

> pg_ctl -D /usr/local/var/postgres -l /usr/local/var/postgres/server.log start
server starting
sh: /usr/local/var/postgres/server.log: No such file or directory

Update 2:

The touch was not successful, so I did this instead:

> mkdir /usr/local/var/postgres
> vi /usr/local/var/postgres/server.log
> ls /usr/local/var/postgres/
server.log

But when I try to start the Ruby on Rails server, I still see this:

Is the server running on host “localhost” and accepting
TCP/IP connections on port 5432?

Update 3:

> pg_ctl -D /usr/local/var/postgres status
pg_ctl: no server running

Update 4:

I found that there wasn’t any pg_hba.conf file (only file pg_hba.conf.sample), so I modified the sample and renamed it (to remover the .sample). Here are the contents:

 # IPv4 local connections:
 host    all             all             127.0.0.1/32           trust
 # IPv6 local connections:
 host    all             all             ::1/128                trust

But I don’t understand this:

> pg_ctl -D /usr/local/var/postgres -l /usr/local/var/postgres/server.log start
server starting
> pg_ctl -D /usr/local/var/postgres status
pg_ctl: no server running

Also:

sudo find / -name postgresql.conf
find: /dev/fd/3: Not a directory
find: /dev/fd/4: Not a directory

Update 5:

sudo pg_ctl -D /usr/local/var/postgres -l /usr/local/var/postgres/server.log start
Password:
pg_ctl: cannot be run as root
Please log in (using, e.g., "su") as the (unprivileged) user that will own the server process.

Update 6:

This seems odd:

> egrep 'listen|port' /usr/local/var/postgres/postgresql.conf
egrep: /usr/local/var/postgres/postgresql.conf: No such file or directory

Though, I did do this:

>sudo find / -name "*postgresql.conf*"
find: /dev/fd/3: Not a directory
find: /dev/fd/4: Not a directory
/usr/local/Cellar/postgresql/9.0.4/share/postgresql/postgresql.conf.sample
/usr/share/postgresql/postgresql.conf.sample

So I did this:

egrep 'listen|port' /usr/local/Cellar/postgresql/9.0.4/share/postgresql/postgresql.conf.sample
#listen_addresses="localhost"        # what IP address(es) to listen on;
#port = 5432                # (change requires restart)
                # supported by the operating system:
                #   %r = remote host and port

So I tried this:

> cp /usr/local/Cellar/postgresql/9.0.4/share/postgresql/postgresql.conf.sample /usr/local/Cellar/postgresql/9.0.4/share/postgresql/postgresql.conf
> cp /usr/share/postgresql/postgresql.conf.sample /usr/share/postgresql/postgresql.conf

I am still getting the same “Is the server running?” message.