Networker shouldn't touch /etc/network/interfaces in a local environment

[Jesse Meek]

Steps to reproduce on trusty 13.04:

# create and start container
1. sudo lxc-create --name c1
2. sudo lxc-start --name c1

# get container ip
3. sudo lxc-ls --fancy

# bootstrap local env and manually provision container
4. juju bootstrap
5. juju addmachine ssh:ubuntu@[container.ip]

# destroy lxc
6. sudo lxc-stop --name c1
7. sudo lxc-destroy --name c1

You now have a broken network configuration. Restart your computer and you should be greeted by a message about the missing network configuration. You should now be unable to connect to the internet. To recover the network:

sudo restart network-manager

# or
sudo start network-manager

# or
sudo /etc/init.d/networking force-reload

# get indicator running in unity panel
/usr/bin/nm-applet

# fix boot time network config issue by adding the following to /etc/network/interfaces
auto lo
iface loinet loopback

[Dimiter Naydenov (dimitern)]

The problem stems from the recent changes in the networker worker. It's too eager to reconfigure /etc/network/interfaces file to include existing NICs config from /etc/network/interfaces.d/*.cfg. This is OK for MAAS and possibly other providers, but not for the local provider, as we shouldn't touch the users' network config like that.

[Dimiter Naydenov (dimitern)]

Easier steps to reproduce this, without breaking your networking setup (hopefully):
1. $ sudo cp /etc/network/interfaces /etc/network/interfaces~
2. Bootstrap a local environment with default config
3. After machine-0 is running in $ juju status, ensure the /etc/network/interfaces and /etc/network/interfaces~ differ
4. Destroy the environment and replace your interfaces file with the backup (no need to start or stop anything I think), possibly also removing /etc/network/interfaces.d/*.cfg the networker created.

[Michael Foord (mfoord)]

https://github.com/juju/juju/pull/477