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Date: Tue, 1 Apr 2014 16:18:19 +0200
From: Michael Olbrich <m.olbrich@pengutronix.de>
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Subject: Re: [ptxdist] machine-id
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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.

Michael

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