[Bug 388060] Re: netboot insall of live cd results in a manual network interface configuration

[Thomas Hood]

I have linked bug #1013843 to this one but I'd like to point out a few
differences.

* Bug #1013843 was filed against Quantal.  The bug didn't affect Precise.
* Quantal has resolvconf. So does the Quantal Desktop live CD. So did Precise. Earlier Ubuntus didn't.
* The problem is observed at the late_command stage rather than after reboot.

Nevertheless I think it's useful to address that bug along with this one
(#388060): both reports lead to the conclusion that the handling of
network configuration and nameserver information from stage to stage
needs to be debugged such that it is correct in all scenarios, including
that of netbooting a live CD to install Ubuntu to a local disk, running
late_command, and rebooting into the installed system.

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https://bugs.launchpad.net/bugs/388060

Title:
  netboot insall of live cd results in a manual network interface
  configuration

Status in Ubiquity:
  New
Status in “casper” package in Ubuntu:
  Triaged

Bug description:
  Binary package hint: casper

  When netbooting the live CD over NFS, the network connection must be
  preserved throughout the live session so that the filesystem remains
  accessible. Currently, this is achieved by adding the following lines
  to /etc/network/interfaces which prevents network manager from
  attempting to reestablish a connection once the desktop finally
  appears:

    auto eth0
    iface eth0 inet manual

  These lines are added by casper in a script called 23networking. Here
  are a few relevant lines from the script:

      if [ -z "${NETBOOT}" ]; then method="dhcp"; else method="manual"; fi
      if [ "$method" != dhcp ] || [ ! -x /root/usr/sbin/NetworkManager ]; then
          # ...       
          cat >> "$IFFILE" <<EOF
  auto $i
  iface $i inet $method

  EOF
      fi

  So, this at least enables the live cd environment to be loaded over
  NFS. However, the problem is that this later gets propagated to the
  installed environment if ubiquity is called. This is done by the
  install.py script and here are the relevant lines from the script:

          for path in ('/etc/network/interfaces', '/etc/resolv.conf'):
              if os.path.exists(path):
                  shutil.copy2(path, os.path.join(self.target, path[1:]))

  In the most common general case, this is the desired behavior so that
  the user's network configuration is propagated from the live to the
  installed environment. However, in the case of netbooting the live cd,
  this is not necessarily the case because this environment needs to
  make assumptions about the network which might not apply anymore once
  the system boots from a drive rather than from the network.

  I suspect the behavior should be that a best effort should be done
  when attempting to propagate the network configuration from the live
  environment when netbooting. This would mean preserving the
  configurations for all the network interfaces except the one used to
  mount the filesystem over NFS. The reasoning is that some assumptions
  were made about that interface which were only relevant in this
  context, so all bets are off about preserving that configuration.

  In order to achieve this desired behavior, I would suspect that casper
  would need to communicate somehow to ubiquity that a particular part
  of the network configuration should not be propagated to the installed
  environment. This could probably be accomplished by using the
  configuration file as the communication interface. For example, the
  interfaces file could look something like:

    # BEGIN IGNORE
    auto eth0
    iface eth0 inet manual
    # END IGNORE

  Then, ubiquity could easily parse that out when propagating the
  network configuration from the live to the installed environment.

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