Shared memory and Mac OS X

The problem with not being able to set shmmax and shmall in a startup script
in Mac OS X is not that you are setting them too late in the boot process.
It is that you can set them only once. In fact, you can set them from a
terminal window after booting and logging in - as long as they haven't
already been set.

If you comment out the sysctl's for shmall and shmmax in /etc/rc, reboot,
then log in and bring up a terminal window, you will see that they are set
to -1. You can then set them to whatever you want (as root of course).
However, if you try to set the value again, the first value remains set.

Unfortunately, this doesn't help much, as Apple's default /etc/rc sets
values. If you comment out these, you can set the values in a startup
script, but you're still screwed when the next update re-enables the
settings in /etc/rc, which are set before SystemStarter is called. I guess
the best you can do is have a startup script that notifies you if the values
are wrong.

Wes