[CentOS] How to start a script to complete configuration

[Leon Fauster]

Am 08.11.2016 um 16:47 schrieb cpolish at surewest.net:
> On 2016-11-07 14:35, Bernard Fay wrote:
>> Hi,
>> 
>> We have a virtual environment based on XenServer. In this environment I
>> defined a template for CentOS 7 servers.
>> 
>> I would like to start a script a boot time to complete the configuration of
>> new VMs based on this template. How can I have a script started before any
>> login prompt to ask question to the user to complete the configuration such
>> as hostname, IP address, etc?
> 
> Hi Bernard,
> 
> My first impulse was "don't!", and that's probably the best
> advise.  A popular model is that the "firstboot" package takes
> care of this at the first user login, and *nix systems sort of
> depend on this "logged in users do stuff" model.
> 
> Even better, use ansible, cfengine, chef, or puppet to automate
> the task of setting things up. This is the _best_ solution and
> you will eventually come back to it.
> 
> But, the darker, cynical part of my brain, the part that says
> "what, you're cutting down on coffee?" part, said "sure you
> can". Here's how it _could_ be done. 
> 
> DON'T DO THIS. TURN BACK NOW.
> 
>    Replace /sbin/init with a shell script that does what you want.
>    It will be the first userland process started, have the console
>    for I/O, and run as root. At completion, restore the original
>    /sbin/init and reboot. Leave no traces behind. Do not document
>    your awful hack, others will use your words against you.



:-) ... kernel parameter init=/root/yourscript

https://www.kernel.org/doc/Documentation/kernel-parameters.txt

--
LF