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Re: starting service order

From: Sebastien ESTIENNE
Subject: Re: starting service order
Date: Tue, 06 Jul 2004 00:11:44 +0200
User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; fr-FR; rv:1.7) Gecko/20040616

To provide such a service, you should define:

1) the ability for a dependency to fail
Yes that's i was asking if this feature exist, it could be implemented like this

depends on apache_bin can fail or a new keyword that would do the same thing named "before"

2) a kind of ordering, or at least, the ability to not startup the
subsequent service in the list if the previous did not already completed
to startup _without_ using a dependency
it could be implemented by keywords like before/after
Gentoo linux already provide this functionnality (look here: )
you can define order with before after
dependencies need/use and also provide

for example you can say that qmail "provide mta" and "need  net"
and that nagios "need mta"

so the system knows that he must start qmail before nagios (if you had use the "use" keyword instead of "need" it means that qmail can fail it's okà

"provide" is also because you can say that many service provide the same functionnality, eg: mta -> qmail, postfix, exim

3) some tool to easily rearrange the services (a chkconfig-like tool) 4)
the ability tu support different runlevels
I wrote this tool, it was easy, i just modified the default tool from gentoo (it was just a matter of 5 lines)
I did it like this:
in /etc/monitrc i added  "include /etc/monit.d/autostart/*"
in /etc/monit.d/ i put a file by service (eg: apache postfix mysql)
and the tool just write or remove a link from /etc/monit.d/ in /etc/monit.d/autostart
so i have the exact same functionnality as a tool like chkconfig
(i don't know if you use gentoo, but now i add services like this: rc-update add apache monit)

you said that monit is only good in specialized situation, or when customized, it's true, but you can define default and then allow the user to provide custom settings without modifying the default install, using include: the default, would only check for pid, and listening port and then the user can overide things or adding things by including his configuration:
/etc/monit.d/system/SERVICE <- contain all default service config
and each SERVICE contain a line like this at the end: include /etc/monit.d/user/SERVICE so when a user want to customized apache for example, he just have to create a file /etc/monit.d/user/apache

I think that monit can remplace the default system, because the onlyt things that the default init system has to do, is stating/stopping system in the right order nothing more
and i don't see why monit couldn't do this?
for example djb's daemontools where built to manage services (they manage qmail/djbdns) and monit seems to be a daemontools++. too bad he also missed the ability to define services start order...

Sebastien ESTIENNE
Administrateur Système et Réseaux

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