I just wasted a couple hours trying to determine why an EXEC_BACKEND build would randomly fail on Fedora Core 4. It seems the reason is that by default, recent Linux kernels randomize the stack base address --- not by a lot, but enough to cause child processes to sometimes be unable to attach to the shared memory segment at the same place the postmaster did.
You can work around this by doing (as root) echo 0 >/proc/sys/kernel/randomize_va_space before starting the postmaster. You'll probably want to set it back to 1 when done experimenting with EXEC_BACKEND, since address randomization is a useful security hack. Just seems like something that should be in our archives ... regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 4: Have you searched our list archives? http://archives.postgresql.org