Re: what binds to port
On Sun, Aug 01, 2021 at 10:41:13AM -0400, songbird wrote:
> mick crane wrote:
> > Doh! discovered have to restart scanbd.service after changing config
> > file.
> > You'd have thought I would know that.
>
> some will restart automatically when their config file changes
> and others don't. you have to know which do and which don't
> since this isn't a universal feature yet.
Very few programs poll for changes to their configuration files. That
would be a sloppy design.
If a program runs as a daemon (really running, i.e. you can see the
process in the output of ps -ef), and you change its configuration file,
you will typically need to take some action to notify the daemon that a
change has occurred. This action may be sending a SIGHUP to the running
daemon, or it may be restarting the daemon.
If on the other hand a program is *not* continuously running as a daemon,
but is instead started on demand (e.g. by inetd or by systemd's socket
activation), then there's no need to take any action when the configuration
is changed. The next instance of the program that gets launched will
by necessity read the configuration file.
So, in almost all cases, it's sufficient to figure out which of these
two designs you're dealing with. Ideally, the documentation (the man
page) of the daemon will tell you. In some cases, there are multiple
ways the service can be implemented (sshd comes to mind), and so the
man page has to list *both* possibilities, and *you* as the sysadmin
have to know which one is actually being used on your system.
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