Question

We have about 40 computers running identical hardware and software. They all run Ubuntu 11.10. They all have just one user account to log in. The .profile file is set up to launch a daemon process. The code for the daemon is written in C.

Once in a few weeks, we get a report that the daemon is no longer running. This does not happen on all computers but just one or two. We cannot reproduce the problem consistently.

Looking at the code, the application quits when it receives either SIGHUP or SIGTERM.

As I understand, SIGHUP is generated when a user logs off. In our case, the user never logs off. I am wondering if it is possible that SIGHUP could have been generated for some other reason. Any other thought would be appreciated.

Answer 1

Signals can be sent using kill utility or kill syscall.
Of course, you can try and find out who is sending that signal or disconnecting your terminals or network connections, but there is simpler practical way to fix your problem.

When code is supposed to run as a daemon, but really isn’t (just like yours), there is a wrapper that can turn any program into daemon. Surprise – this wrapper is called daemon! It has lots of options, probably most importantly for you, option to automatically restart your utility should it ever die for any reason.

If this command is not installed on your Ubuntu, just sudo apt-get install daemon, and man daemon to get started.