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Re: hotplugging /e/n/i "auto" interfaces

On Thu, Apr 08, 2004 at 12:34:16PM +0100, J.D. Hood wrote:
> When installing hotplug one may select one of three policies
> governing which network interfaces are ifup'ped when they are
> created by the kernel.  One of these policies is for hotplug to
> ifup all interfaces listed after the "auto" keyword in
> /etc/network/interfaces.  Can someone please explain to me what
> sense this makes?

I would expect that the usage of auto here means
"Bring up this interface automatically". Certainly it makes sense
to me that an interface marked 'auto' should come up when it is
first available, either boot or hotplug time.

> So far as I can see, it makes no sense.  Interfaces listed after
> the "auto" keyword are brought up by the "ifup -a" command in
> /etc/rcS.d/S40networking.  This provides a way of listing those
> interfaces to be brought up during the boot sequence -- i.e.,
> interfaces which _aren't_ to be left to hotplug or to the admin to
> bring up later.  Typically this list includes lo and the names of
> interfaces that are known to be present at boot time.

Nothing in the interfaces(5) manpage suggests that this is only
for boot-time, it only mentions that boot-time does this.

> The interfaces brought up by S40networking obviously don't also need
> to be brought up by S40hotplug.

I can't see why anyone would _object_ to this usage. After all,
it's not like ifup -a breaks any of your interfaces that are
already running, right?

> It _might_ make sense for hotplug to offer a policy of ifup'ping
> those interfaces _not_ listed as "auto" in /etc/network/interfaces.
> But I do not see the sense in ifup'ping those interfaces that _are_
> listed as "auto".

> I contacted the hotplug maintainer about this and he says that he
> added this feature because "people wanted it".  My suspicion is
> that those who asked for this feature don't understand what "auto"
> means in the context of /etc/network/interfaces and that they are
> asking for the system to be changed so that it conforms to their
> misunderstanding.  If my suspicion is correct then we'll soon see
> a bug filed against netbase complaining that "auto" interfaces
> shouldn't be brought up in S40networking because they are already
> brought up by hotplug, and once this bug is closed we will have to
> add a _new_ feature to ifupdown to do what "auto" did before.

I like that idea, for systems which use hotplug and therefore get
hotplug events for all the cards in the system already at boot...

Move hotplug before networking in the boot sequence, and then
when networking kicks in, it'll up all the virtual and other
non-physical interfaces...

> Of course I could be wrong about this and I would welcome enlightenment.

> If it turns out that my suspicion is true then I will ask the hotplug
> maintainer to remove the "hotplug auto interfaces" policy option.

I'm in favour of this being the interpretation of 'auto', that
interfaces so marked are brought up when they can be.

If that's not what it _has_ been, well, I guess it's not been
an issue before hotplug?

Maybe for a boot-time only option, it should be 'boot' not
'auto'? (I think someone suggested up-at-boot in the previous
thread on this topic)

Paul "TBBle" Hampson, MCSE
7th year CompSci/Asian Studies student, ANU
The Boss, Bubblesworth Pty Ltd (ABN: 51 095 284 361)

"No survivors? Then where do the stories come from I wonder?"
-- Capt. Jack Sparrow, "Pirates of the Caribbean"

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