weird fatal error starting postmaster

Upgraded to current postgres via the RPM packages.
postgresql-devel-6.5.3-1
postgresql-jdbc-6.5.3-1
postgresql-odbc-6.5.3-1
postgresql-perl-6.5.3-1
postgresql-python-6.5.3-1
postgresql-server-6.5.3-1
postgresql-6.5.3-1
postgresql-tcl-6.5.3-1
postgresql-test-6.5.3-1

I'm of course on RedHat Linux. Specifically v6.0 .Dual processor PII, running SMP kernel 2.2.5-22smp
I do (in inittab)
/bin/su - postgres -c "/usr/bin/postmaster -D/var/db" >>/var/log/postgres.log 2>&1 </dev/null

and postgres.log says:

IpcMemoryCreate: shmget failed (Identifier removed) key=5432010, size=120, permission=700
IpcMemoryIdGet: shmget failed (Identifier removed) key=5432010, size=120, permission=0
IpcMemoryAttach: shmat failed (Invalid argument) id=-2
FATAL 1:  AttachSLockMemory: could not attach segment

Hmm.  Could this somehow be that user postgres has no permission to create an IPC memory queue?
thought all users could...
thoughts and direction appreciated