On Thu, Jan 27, 2011 at 2:06 PM, Raymond O'Donnell <rod at iol.ie> wrote:
> On 27/01/2011 20:35, Christopher Browne wrote:
>> Raymond O'Donnell<rod at iol.ie>  writes:
>>> Hi all,
>>>
>>> Apologies for the entry-level question.... I'm getting to grips with
>>> Slony on Linux for the first time (have been running it on Windows for a
>>> while).
>>>
>>> The slon program is described in the docs as a daemon.... so does that
>>> mean that when run it's supposed to detach from the terminal and run
>>> independently, continuing to run when I log out?
>>>
>>> If not, what do people usually do?
>>
>> Erm, slon is logically a daemon, so it's *like* those programs that
>> detach themselves.  And yes, it's supposed to run independently, because
>> it's not much good if it stops replicating when you log out :-).
>>
>> It's not *formally* implemented as a daemon, though - we didn't go the
>> whole 9 yards to make it detach itself that way.
>
> Hi Christopher, thanks for the reply. That's what I was wondering about
> - experimentation showed that the slon process did indeed disappear when
> I logged out. :-)
>
> Just curious - why did you go this route with the implementation.

Actually it's VERY common to implement unix daemons this way, for the
reason mentioned in Christopher's reply, that it makes troubleshooting
easier.  For instance Postgres uses either the pg_ctl wrapper or an
/etc/init.d/postgresql wrapper to daemonize it, but is easily started
in single user mode for troubleshooting.

In fact, according to grep, sort, uniq, and wc, 83 of the 88 daemons
in my /etc/init.d directory have && in them somewhere which is usually
used to detach a process from a terminal in this way.

> I was looking at slon_start.sh, and as far as I can make out (I'm no
> expert in shell scripting) slon just gets pushed into the background;
> won't it then vanish once I log out? - or have I misunderstood the script?

No, it gets pushed into the background and detached as well.