Preventing Shutdown on Active NFS Servers?

Ed Almos asks: "Like many Slashdot Readers, I run a small network at home with a server and a number of desktops. The server holds all our files as NFS shares and doubles as a desktop machine should the need arise. Problems however occur if the server is shut down whilst there are NFS shares in use, the minimum disruption is a crashed desktop and a couple of times I have had to deal with corrupted files. Does anyone know of a way to prevent shutdown of a machine if someone else has drives mounted to its NFS shares ? I have already explored use of the /etc/shutdown.allow file but all this does is determine who can kill the machine. The minimal solution would be something similar to a Microsoft Windows system, where a request to shutdown brings up a warning window that there are users connected to the system, but I am not sure how to achieve this on a Linux system. Ideally I would like to prevent shutdown of a system with active NFS shares altogether, or at least until the user has unmounted and logged off the network."

Comments

Can't do it

[djmitche]

NFS is stateless from the server's perspective. This is done so that the server doesn't have to track the state of a whole fleet of clients (and so that the server can pick up where it left off when it crashes and restarts).

So the server, by design, has no notion of the number / names of users connected to it.

The best you could do would probably be to monitor NFS traffic, and present a dialog on shutdown if there has been any traffic in the last 5 minutes or so.

Re:Implementation

[Glonoinha]

Even better thought, he could decide that there actually is a distinction between server duty and workstation duty and decide which this particular machine is going to pull. If he needs the machine to run as a workstation, quit trying to use an unstable environment as a server. If the files and stability of the system are of any importance whatsoever then it is a server, treat it as such and buy another computer to use as a workstation (they are dirt cheap now.) Pretty simple.

Want to see your uptime and stability rise incredibly on the server? Put it in the closet on a UPS and once it is running turn off the monitor, unplug the keyboard, and tape a piece of cardboard over the power switch so it doesn't get turned off by accident. Where the machine used to sit put a cheap replacement computer to use as a workstation - even new entry level boxes are starting at under $500 fully loaded (a little wimpy, but including all the necessary parts including a monitor) and used hardware has gotten insanely cheap (ie $200 for a full machine that is a generation or two old, PIII .5 to 1GHz range with a CRT.)

That said, I am going to read every post in this thread to get a better understanding of how to do this - now you have my interest up.