[PATCH] Move machine-id to /var

[Alp Toker]

Havoc Pennington wrote:
> On the other hand, if a low-level system component like dbus solves 
> this, then it's just solved and only has to be addressed once when 
> creating a deployment setup - apps above dbus don't need to worry about 
> it or hand-roll their own approach.

I think Robert is onto something here. If the machine ID feature makes 
it into the D-Bus specification, it'll be the first feature that I've 
seen in the spec that requires non-obvious platform-specific code.

Right now, managed D-Bus assemblies can be copied across Linux, FreeBSD, 
Windows and various .NET runtimes without needing to be rebuilt or 
configured at install time.

I have already started work on a managed uuidgen utility and an 
implementation of the relevant interface, but all the time I've been 
writing this code I've been getting seriously bad vibes.

I don't see any good reason or means to reliably persist a "machine" 
uuid since there is no such thing as a "machine" -- CPUs get hotswapped, 
block devices get network mounted, disk images get copied, MAC addresses 
change. This appears to be at best a misnomer, quite possibly a misfeature.

As an implementer of the D-Bus spec, I have concerns about supporting 
it, as a former packager I would be uncertain how to provide the 
semantics you expect and as a system administrator who has deployed 
large networked installations, the last thing I want is another 
non-standard "machine" identifier, especially from what's meant to be a 
simple IPC mechanism package.