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Re: Am I missing something in my understanding here?

Freddy Freeloader wrote:
> The first time I run "/etc/init.d/networking restart" after a reboot I 
> get the same message I would if I ran "ifdown eth0" about eth0 releasing 
> its dhcp address, and I no longer have network connectivity, i.e. the 
> /etc/init.d/networking script does not seem to call ifup -a to restart 
> all network connections.  (I have only one nic on this computer.)  To 
> get network connectivity back I must manually run "ifup etho". 

The problem is rooted in Bug#300937.  It is about how to handle
hotplug network devices.


The default Etch installation configures networking such as you are
seeing now.  But let's back into it from the side.  The configuration

  allow-hotplug eth0

You noted "ifup -a".  But /etc/init.d/networking does call ifup -a.
But looking at the man page for ifup shows:

       -a, --all
              If given to ifup, affect all interfaces marked auto.

So 'ifup -a' only brings up interfaces marked auto but a default Etch
installation sets all interfaces to allow-hotplug.  Now you can see
why restarting networking does not bring up networking.

And in the man page for interfaces it says:

       Lines beginning with the word "auto" are used to identify the
       physical interfaces to be brought up when ifup is run with the
       -a option.  (This option is used by the system boot scripts.)
       Lines beginning with "allow-" are used to identify interfaces
       that should be brought up automatically by various
       subsytems. This may be done using a command such as "ifup
       --allow=hotplug eth0 eth1", which will only bring up eth0 or
       eth1 if it is listed in an "allow-hotplug" line.

> My question is, is this behavior by design, or have I stumbled across a 
> bug? 

I don't know the full history behind this but looking at the
Bug#300937 I assume the design is that network events are now moved
from boot time action to network event time action to support hotplug
network interfaces.  Looking in /usr/share/doc/udev/README.Debian.gz I

  After receiving events about network interfaces, net.agent will call
  ifupdown using the --allow=hotplug option. This makes the program act
  only on interfaces marked with the "allow-hotplug" statement.
  E.g: "allow-hotplug eth0" instead of the usual "auto eth0".

I have not researched further what it would take to trigger udev to
restart networking but I presume there is a path through it that would
do so.  To return to the previous behavior you may change the
allow-hotplug stanzas into auto stanzas and then restarting networking
will restart the network interface.  I would welcome further
information on this area.


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