[Bug 1711760] Re: [2.3] resolv.conf is not set (during commissioning or testing)

[Andres Rodriguez]

** Changed in: maas
    Milestone: 2.3.0 => 2.3.0beta2

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Title:
  [2.3] resolv.conf is not set (during commissioning or testing)

Status in MAAS:
  Confirmed
Status in cloud-init package in Ubuntu:
  Confirmed
Status in resolvconf package in Ubuntu:
  In Progress

Bug description:
  Using MAAS 2.3, during commissioning (and likely in the rest of the
  ephemeral environment) we have noticed that resolv.conf is not set
  with the DNS server.

  That said, during the commissioning process, MAAS does not send any
  metadata to cloud-init to configure the network, rather, we expect the
  image to boot from the network via DHCP. So, cloud-init writes:

  ubuntu at manual:~$ cat /etc/network/interfaces.d/50-cloud-init.cfg
  # This file is generated from information provided by
  # the datasource.  Changes to it will not persist across an instance.
  # To disable cloud-init's network configuration capabilities, write a file
  # /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following:
  # network: {config: disabled}
  auto lo
  iface lo inet loopback

  # control-manual ens3
  iface ens3 inet dhcp
      broadcast 192.168.122.255
      dns-nameservers 192.168.122.2
      gateway 192.168.122.1
      netmask 255.255.255.0

  Which correctly includes the DNS server. However:

  ubuntu at manual:~$ ping google.com
  ping: unknown host google.com

  If restart the interfacE:

  ubuntu at manual:~$ sudo ifdown ens3 && sudo ifup ens3
  ifdown: interface ens3 not configured
  Internet Systems Consortium DHCP Client 4.3.3
  Copyright 2004-2015 Internet Systems Consortium.
  All rights reserved.
  For info, please visit https://www.isc.org/software/dhcp/

  Listening on LPF/ens3/52:54:00:ea:57:31
  Sending on   LPF/ens3/52:54:00:ea:57:31
  Sending on   Socket/fallback
  DHCPDISCOVER on ens3 to 255.255.255.255 port 67 interval 3 (xid=0x14eb0354)
  DHCPDISCOVER on ens3 to 255.255.255.255 port 67 interval 4 (xid=0x14eb0354)
  DHCPREQUEST of 192.168.122.195 on ens3 to 255.255.255.255 port 67 (xid=0x5403eb14)
  DHCPOFFER of 192.168.122.195 from 192.168.122.2
  DHCPACK of 192.168.122.195 from 192.168.122.2
  Restarting ntp (via systemctl): ntp.service.
  bound to 192.168.122.195 -- renewal in 290 seconds.

  ubuntu at manual:~$ cat /etc/resolv.conf
  # Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
  #     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
  nameserver 192.168.122.2
  search maas

  ubuntu at manual:~$ ping google.com
  PING google.com (216.58.192.46) 56(84) bytes of data.
  64 bytes from mia07s46-in-f14.1e100.net (216.58.192.46): icmp_seq=1 ttl=52 time=7.47 ms
  ^C
  --- google.com ping statistics ---
  1 packets transmitted, 1 received, 0% packet loss, time 0ms
  rtt min/avg/max/mdev = 7.472/7.472/7.472/0.000 ms

  As such, this either seems like a bug in Ubuntu, or caused by cloud-
  init when writing e/n/i.d/50-cloud-init.cfg

  ubuntu at manual:~$ dpkg -l | grep cloud-init
  ii  cloud-init                       0.7.9-153-g16a7302f-0ubuntu1~16.04.2       all          Init scripts for cloud instances
  ii  cloud-initramfs-copymods         0.27ubuntu1.4                              all          copy initramfs modules into root filesystem for later use
  ii  cloud-initramfs-dyn-netconf      0.27ubuntu1.4                              all          write a network interface file in /run for BOOTIF

  ubuntu at manual:~$ uname -a
  Linux manual 4.4.0-92-generic #115-Ubuntu SMP Thu Aug 10 09:04:33 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
  ubuntu at manual:~$ lsb_release -a
  No LSB modules are available.
  Distributor ID: Ubuntu
  Description:    Ubuntu 16.04.3 LTS
  Release:        16.04
  Codename:       xenial

  ubuntu at manual:~$ pastebinit /var/log/cloud-init.log
  http://paste.ubuntu.com/25342738/
  ubuntu at manual:~$ pastebinit /var/log/cloud-init-output.log
  http://paste.ubuntu.com/25342740/

  Related bugs:
   * bug 1714308: dns does not work in initramfs after configure_networking
   * bug 1713803: replacement of resolvconf with systemd needs integration

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