I have a fairly simple question, but I need a very sure answer. If close(2) is called on the last file descriptor that references a standard file, are dirty pages associated with that file's buffers automatically queued for writing, in a similar manor to sync(2)? Everyone I've talked to has said "I think so," but I'm looking for something a bit stronger. The reason I ask is this: We've got an OS X box in a very remote location that has pretty flaky power. We've got a UPS, but there are times when even that isn't enough. The problem is if the UPS software shuts down the machine, it will not restart once power comes back. The *only* way to get it to restart is to press the power button, and trust me-- given where this machine is, that's a serious pain the butt. The same behavior is displayed with halt(8) and any other number of commands I've tried. So my thought is to modify the UPS scripts to "almost" shut the machine down, and then just let the power fail. The "automatically restart on power failure" should then catch the machine and allow it to come back on its own. Of course, the thought of just ripping the power out from under a machine will give most admins the willies, so I was trying to come up with a way to put the system in an absolute minimal state before allowing the power to be cut. Sending init(1) a SIGTERM to dump the system into single user mode seems like a good bet. That leaves the system with nothing but init and a shell running, both of which will sit there and do nothing. In looking at how init(1) brings the system down, I noticed that it does the standard "kill everything" sequence of SIGHUP, wait, SIGTERM, wait, SIGKILL. It doesn't actually call sync(2), however, which brings up the question: does it need to? If the processes are allowed to exit or are killed, and their file descriptors are closed out as the processes are cleaned up, are the dirty pages associated with such files written out? Or do they just sit in memory waiting for something to happen? I can't call sync(8) *after* we get into single-user mode, since the transition will cause init to kill my script. So is this a safe plan, or do I need to worry about dirty pages? -j -- Jay A. Kreibich | Integration & Software Eng. jak@uiuc.edu | Campus IT & Edu. Svcs. <http://www.uiuc.edu/~jak> | University of Illinois at U/C _______________________________________________ darwin-kernel mailing list | darwin-kernel@lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.