Shutdown causing reboot in EC2

[Colin Percival]

On 10/28/17 10:21, Rafal Lukawiecki wrote:
>> Technically it's the FreeBSD project's image. :-)
>
> I realise that. I am glad to be using it via the Marketplace so that it enables you and FreeBSD RE to count the popularity of the OS on AWS. I understand you would not get the count otherwise.

Just wanted to be clear. :-)

>> I guess the obvious question here is "what does it mean for a virtual machine
>> to be halted but not powered off”?
> 
> I defer to you and to others who are more experienced than I to answer
> this. The ‘shutdown -h’ behaviour with Amazon Linux and CentOS on AWS is to
> power off. However, if reboot is what is supposed to happen in this case, I
> will gladly adjust to that, although it feels a little odd.

That wasn't so much a technical question as a philosophical question -- we've
inherited shutdown actions from how hardware in the 1980s worked, and since
'shutdown -h' doesn't have any clear meaning in a VM I don't know that anyone
gave it much thought.  Certainly I never did.

I suspect that the difference between Linux and FreeBSD here lies in how our
underlying Xen code handles shutdown events... to be completely frank, I don't
even know which code handles it under Xen HVM.  But it's probably a bad idea
to change it now, since some people have learned the existing behaviour.

-- 
Colin Percival
Security Officer Emeritus, FreeBSD | The power to serve
Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid