Additionally, "ifconfig" no longer shows secondary addresses. Notice
that `10.17.0.6/16` in #7 above is not defined:
root@utl-ubuntu-16-04-x64-50307:~# ifconfig eth0
eth0 Link encap:Ethernet HWaddr 4a:41:c5:1b:8a:a0
inet addr:138.197.91.79 Bcast:138.197.95.255 Mask:255.255.240.0
inet6 addr: fe80::4841:c5ff:fe1b:8aa0/64 Scope:Link
inet6 addr: 2604:a880:800:10::2ced:3001/64 Scope:Global
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:844 errors:0 dropped:0 overruns:0 frame:0
TX packets:653 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:107141 (107.1 KB) TX bytes:91481 (91.4 KB)
** Summary changed:
- 0.7.9-48-g1c795b9-0ubuntu1~16.04.1 with multiple eth0 definitions has no
resolvers
+ Cloud-init update renders secondary addresses ti be incompatible with
standard tools
** Description changed:
+ The change of how cloud-init renders
/etc/network/interface.d/50-cloud-init.cfg, standard tools no longer work as
expected:
+ * resolvconf will nullify nameservers
+ * if* commands ignore secondary addresses
+
+ The rendering is considered dangerous per Debian
(https://wiki.debian.org/NetworkConfiguration), to whit:
+ "Also, ifupdown supports specifying multiple interfaces by repeating iface
sections with the same interface name. The key difference from the method
described above is that all such sections are treated by ifupdown as just one
interface, so user can't add or remove them individually. However, up/down
commands, as well as scripts, are called for every section as it used to be.
+
+ "Note however that this method is dangerous! Certain driver/hardware
combinations may sometimes fail to bring the link up if no labels are assigned
to the alias interfaces. (Seen this on Debian Wheezy and Jessie with
RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 01)
auto-negotiating to 10/full. A similar warning from another person exists in
the history of this page.)
+ "
+
+
+ [ORIGINAL REPORT]
+
Regresion from Bug #1657940.
When provisioning with multiple eth0 addresses, /etc/resolv.conf is
empty:
Consider:
root@tester:~# 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
auto eth0
iface eth0 inet static
address 138.197.98.102
dns-nameservers 8.8.8.8 8.8.4.4
gateway 138.197.96.1
netmask 255.255.240.0
# control-alias eth0
iface eth0 inet static
address 10.17.0.11
netmask 255.255.0.0
Which then yields an empty /etc/resolv.conf:
root@tester:/run/resolvconf# cat interface/eth0.inet
root@tester:/run/resolvconf# 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
The problem is that resolvconfg does pattern matching for eth*.inet. The
second definition of eth0 has no nameserver and therefore overrides the
definition.
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https://bugs.launchpad.net/bugs/1675571
Title:
Cloud-init update renders secondary addresses ti be incompatible with
standard tools
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