Help installing PGSQL 7.1 on Linux

Following the instruction at the top of the 'INSTALL' file, I have
installed PostgreSQL. However, after creating the 'postgres' user
and su[ing] to the postgres user account, according to the
'INSTALL' file, I have to initialized the data base, using the
following command

'/usr/local/pgsql/bin/initdb -D /usr/local/pgsql/data'

After doing so, I get a message that reads:
"This database will be initialized with user name "postgres".
 This user will own all the data files and must also own the server
process.
mkdir: cannot create directory /usr/local/pgsql/data: Permission
denied.
initdb failed
Removing temp file /tmp/initdb.224."

Using the root account to do the installation, I have tried
about three times to get the installation completed, but I have had
the same problem all three.

Does anyone know what could be happening?

Thanks in advance

=======================================
                    PostgreSQL Installation Instructions

Short Version

./configure
gmake
gmake install
adduser postgres
su - postgres
/usr/local/pgsql/bin/initdb -D /usr/local/pgsql/data  <<== PROBLEM IS
HERE
/usr/local/pgsql/bin/postmaster -D /usr/local/pgsql/data >logfile 2>&1 &

/usr/local/pgsql/bin/createdb test
/usr/local/pgsql/bin/psql test