Interesting new feature
jdennis at redhat.com
Fri Apr 24 00:57:13 CEST 2009
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
% 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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