Interesting new feature

[John Dennis]

Arran Cudbard-Bell wrote:
> Interesting indeed. I can see a use for this. How do you initiate the
> HUP ? Via the radmin tool ?
>   
HUP is a Unix signal, originally meaning "Hang Up" but since has been 
co-opted to mean "reload your configuration" when the signal is sent to 
a service (e.g. a daemon). Note, reload is significantly different than 
restart, during a reload the service continues to run whereas a restart 
the existing process is terminated and restarted. Unix signal are sent 
to a process via the kill() function or the kill command (historically 
signals were often used to kill a process, hence the name, however a 
better name might be send_signal(), but history lives on).

So to send a HUP to radiusd you need to know the process id (pid) of the 
radiusd service, let's say it's 1234:

% kill -HUP 1234

-or-

% kill -HUP `pidof radiusd `

Most SysV init scripts support the reload command, the init script knows 
the pid of the service and whether it's running, thus the preferred way 
to send a HUP reload is:

% service radiusd reload

Of course radmin and the other control features should accept triggering 
a reload and I'm sure Alan has added this, but it probably won't be via 
a  HUP signal, I expect the control socket will receive a reload command 
which calls the same function the signal handler invokes when it 
receives a HUP signal (actually the reload won't occur in the signal 
handler, rather the signal handler will set a flag).

-- 
John Dennis <jdennis at redhat.com>

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