Used the following to modify the shmmax kernel parameter in Fedora 13 after updating postgresql on a machine running WiKID for two-factor authentication.

Modifies the parameter:
# sysctl -w kernel.shmmax=67108864
Changes the parameter so a reboot is not required.
# sysctl -p /etc/sysctl.conf

To keep the new setting after rebooting:
# vi /etc/sysctl.conf
…
kernel.shmmax=67108864
…