Re: [Xen-users] how to start VMs in a particular order

[lee <lee@xxxxxxxxxxxxxxx>]

Simon Hobson <linux@xxxxxxxxxxxxxxxx> writes:

> Eg, just looking on a random box, ntp has this section :
>> ### BEGIN INIT INFO
>> # Provides:        ntp
>> # Required-Start:  $network $remote_fs $syslog
>> # Required-Stop:   $network $remote_fs $syslog
>> # Default-Start:   2 3 4 5
>> # Default-Stop: 
>> # Short-Description: Start NTP daemon
>> ### END INIT INFO
>
> Change Required-Start to be "$network $remote_fs $syslog $wait_for_dns", 
> rerun the init-script setup, and then you have a system that would pause for 
> the DNS to be available before it started the ntp service.

You'd also have to specify which other hosts to notify and which of all
the hosts need to wait for which others.

Think it further, and you might want something like a daemon running
somewhere which receives information from all hosts about which services
they have started and tells hosts what to start next.  You'd have a
central place to specify all the dependencies, only one file to edit
and to rule them all.

Once you have that, you might want the daemon to monitor the hosts and
tell you when a service is down or something else goes wrong.

Something like a meta-systemd ...


-- 
Knowledge is volatile and fluid.  Software is power.

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