Bug#745876: Please create /etc/machine-id if it does not exist

[Santiago Vila]

On Mon, 28 Apr 2014, Michael Biebl wrote:

> Am 28.04.2014 17:51, schrieb Santiago Vila:
> > For now, /etc/machine-id is a configuration (or state) file for the
> > systemd package. Documentation about machine-id even says that
> > removing the file on reboots is mostly harmless (you could have a
> > different machine-id every time the machine boots and nothing bad
> > would happen).
> 
> Hm, I don't see this recommendation anywhere. The machine-id man page
> [0] at least doesn't give any advice like this.

(Hmm. Maybe you misread "Documentation" as "Recommendation"?)
It's certainly not a recommendation, nor an advice. It's just something
which is possible to do for stateless systems:

"Optionally, for stateless systems, it is generated during runtime at
boot if it is found to be empty."

(See the same manpage URL that you quoted at the end)

> If you are going to change machine-id, this will treat old journal files
> as coming from a different system. I wouldn't consider that a harmless
> consequence.

Presumably, if you purge (not just remove) systemd to install another
init system, you are not interested in those journal files.

> [...]
> > On the other hand, if you can show me another init system (which is
> > not systemd) also using /etc/machine-id, we can reconsider about this.
> 
> The reason why we want to see /etc/machine-id in base-files is actually
> because it is not only used by systemd, but e.g. also by dbus.

That's fine, but the issue here (I mean: the reason why I think this
has no place in base-files) is not "used by systemd vs used by some
other package as well" but "used by at least one essential package vs
not used by any package which is essential".

> Say you've installed both dbus and systemd, dbus will read and use
> /etc/machine-id. If you now purge the systemd package (and
> /etc/machine-id along with it), this will confuse dbus.

Well: How would you fix that if base-files didn't exist?

If the only solution is not to remove machine-id, then piuparts is
wrong and keeping machine-id in the system should be allowed.