Problem starting postmaster

Hello there,

I am migrating from MySQL to PostgreSQL.
I have built pgsql 7.0.3 on Redhat 7.0.
All of the nevironmental variables have been
set properly. When I try to start the database
server using the following

bash-2.04$ /usr/local/pgsql/bin/postmaster

I get

IpcMemoryCreate: shmget failed (Identifier removed) key=5432010,
size=144, permission=700
This type of error is usually caused by an improper
shared memory or System V IPC semaphore configuration.
For more information, see the FAQ and platform-specific
FAQ's in the source directory pgsql/doc or on our
web site at http://www.postgresql.org.
IpcMemoryIdGet: shmget failed (Identifier removed) key=5432010,
size=144, permission=0
IpcMemoryAttach: shmat failed (Invalid argument) id=-2
FATAL 1: AttachSLockMemory: could not attach segment

I have read the docs. The only probable cause is the
lack of SYS V IPC support or small size of configured
shared memory in the kernel. However, neither one of
these suggestions applies to my case. I have even tried

bash-2.04$ /usr/local/pgsql/bin/postmaster -B 64

and the problem still persists.

Can somebody shed some light here?

Thanks,
HY