initlocation and createdb

I'm having trouble setting up databases in a new location. In particular, I
do the following:

[postgres(at)whopper pgdata]$ export PGDATA2=/home/pgdata
[postgres(at)whopper pgdata]$ initlocation PGDATA2
The location will be initialized with username "postgres".
This user will own all the files and must also own the server process.

Fixing permissions on pre-existing directory /home/pgdata
Creating directory /home/pgdata/base

initlocation is complete.
You can now create a database using
CREATE DATABASE <name> WITH LOCATION = 'PGDATA2'
in SQL, or
createdb <name> -D 'PGDATA2'
from the shell.

[postgres(at)whopper pgdata]$ createdb optodb -D 'PGDATA2'
ERROR: The database path 'PGDATA2' is invalid. This may be due to a
character that is not allowed or because the chosen path isn't permitted for
databases
createdb: database creation failed
[postgres(at)whopper pgdata]$

The permissions for /home/pgdata are

drwx------ 3 postgres postgres 4096 Jun 13 16:41 pgdata

What am I doing wrong? Is /home not permitted for databases? If so, why
not, and what is permitted?

Thank you for any help.

David Barnes