How do I increase shared memory in 4.7

[Hal Lynch]

I am running postgres on my 4.7 system and I need more
shared buffer space.  If I set the # of shared buffers in
postgres to what I want it won't start because I need more
shared buffers than are available from the system.

I have tried raising kern.ipc.shmmax from 160000000 to
256000000 using sysctl but it doesn't seem to make a
difference.

Can anyone help?

hal