Mac OS X 10.3 and SYSV shared memory settings

Kevin Murphy · *nix forums beginner Joined: 11 Mar 2005 Posts: 30

Because I was just burned by this, I'd like to remind OS X users that
OS 10.3 (Panther) may be a less desirable platform than 10.2 for
running PostgreSQL and other applications that benefit from customizing
SYSV shared memory settings.

The problem is that in 10.3, there unbelievably seems to be no reliable
way to customize the SYSV shared memory settings such that the settings
are preserved across OS updates (10.3.6 to 10.3.7, e.g.)!

The following reminder from the PG 8.0 manual (thanks to whomever put
this in) also applies to PG 7.4.X, and it is incredibly important:

"In OS X 10.3, these commands [shared memory sysctl commands] have been
moved to /etc/rc and must be edited there. You'll need to reboot to
make changes take effect. Note that /etc/rc is usually overwritten by
OS X updates (such as 10.3.6 to 10.3.7) so you should expect to have to
redo your editing after each update."

If someone has a solution to this problem, please let me know. In the
meantime we'll have to implement a cron-driven alert and a policy
change, hope that transitioning to a new sysadmin at a later date does
not screw us, and pray that 10.4 provides a solution to this problem.
A simple change to /etc/rc on Apple's part seems to be all that would
be required - it already executes sysctl commands from a user-defined
/etc/sysctl.conf file, but the shared memory settings can only be set
*once*, and /etc/rc happens to set the defaults before reading
/etc/sysctl.conf. I can have a cron job remove the shared memory
sysctls in /etc/rc if they reappear, but that would be a decidedly
imperfect kludge.

Kevin Murphy

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