[systemd-devel] Question about systemd-firstboot

[Francis Moreau]

On Thu, Mar 9, 2017 at 3:10 PM, Zbigniew Jędrzejewski-Szmek
<zbyszek at in.waw.pl> wrote:
> On Thu, Mar 09, 2017 at 10:48:03AM +0100, Francis Moreau wrote:
>> Hello,
>>
>> I'm puzzled about systemd-firstboot service.
>>
>> In my understanding this service is ran only during the firstboot. The
>> firstboot condition is detected with the presence of /etc/machine-id
>> file.
>>
>> If this file is not present then it's assumed to be a first boot and
>> systemd-firstboot.service is ran and will create the machine-id file.
>>
>> Now the thing is that I dont see how systemd-firstboot.service can
>> have a chance to be started because if /etc/machine-id is missing the
>> whole boot is failing due to journald requiring /etc/machine-id.
>>
>> Could anybody give me some clues ?
>
> machine_id_setup() is called from main(). So pid1 should set up
> /etc/machine-id if possible (/etc is wriable) before it starts the
> firstboot services.
>

For regular boots /etc is always RO when systemd is started, at least
in my understanding.

Just give it a try, remove /etc/machine-id and reboots, you'll see
that journald will fail.

Cheers.
-- 
Francis