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From: "Gieseler, Christian" <CG@eks-engel.de>
Date: Wed, 2 Apr 2014 14:25:29 +0000
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Subject: Re: [ptxdist] machine-id
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Hi Michael,

> -----Original Message-----
> From: ptxdist-bounces@pengutronix.de [mailto:ptxdist-
> bounces@pengutronix.de] On Behalf Of Michael Olbrich
> Sent: Tuesday, April 01, 2014 4:18 PM
> To: ptxdist@pengutronix.de
> Subject: Re: [ptxdist] machine-id
> 
> On Mon, Mar 31, 2014 at 01:13:28PM +0000, Gieseler, Christian wrote:
> > while thinking how to preserve the existing machine-id after an
> > complete update I had I look how this is generated. In the rc-once.d
> > folder there is a script generating an id and systemd also has the
> > capability to generate one and obviously does check for a valid
> > machine-id and regenerates one in case of an invalid/non exisiting one.
> > Looking into the dependencys  the ptxdist machine-id script is selectd
> > with systemd. Is the existance of the ptxdist machine-id necessary if
> > systemd takes care of the machine id?
> > And finaly coming back to the original question what is the best way
> > to preserve the machine-id? Patching Systemd to change the hardcoded
> > path? Or are there other smarter solutions?
> 
> The machine-id is read very early, so even if you change the path in systemd,
> so the path must be in the rootfs and is probably overwritten during a
> complete update.
> You could explicitly save the machine-id before an update and copy it back
> afterwards.
> If you have an initrd then you could bind mount  your machine-id to
> /etc/machine-id before starting systemd.

Ok, thats clear and easy to implement.

Can you explain why one needs the script /etc/rc.once.d/machine-id if the machine id is generated by systemd?

Best regards
Christian

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