start daemon program by general user in fc-4

Hello!

I want to start daemon program by general user in fedora core 4 system's
startup script .
for example, I add one line in /etc/rc.local:
	su postgres -c 'postmaster -D /home/data'

but this failed, and the message is "su: /bin/sh permission denied"

When i login the system using root, i can run this command.
I think this problem related to the fc-4 system, because i can do the
same thing under redhat-9 system.
Can you give me help? thanks!

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