Suddenly /dev/null became a regular file

I was doing a routine task – preparing a new CentOS server – today and ran into quite obscure problem.

I was at the point where I needed to configure VPN link but OpenVPN wouldn’t let me daemonize itself. It complained in the logs basically saying that the problem was this:

openvpn[4738]: daemon() failed: No such device (errno=19)

That’s weird. After an hour of troubleshooting this issue on the server I took it to #openvpn@irc.freenode.net where dazo, the channel operator, pointed out that some people previously had have a similarly looking problem, and that if /dev/null was involved it might be a similar or exactly that kind of problem.

I checked /dev/null with stat utility and it was indeed just a regular file. WHOA. This is a production server that doesn’t see software updates, tested and works for the most part as a clock. Utterly inexplicable at this point to me but I don’t have time to research this right now. I just wanted to make a post about it to remember to look into this later, because this is quite interesting and doesn’t happen very often. In fact, I’ve been working with Linux for at least 5 years now, and I’ve never seen anything of the sort. Not even my more than I am experienced colleagues.

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