Comment 2 for bug 2011783

>> Are you wanting to disable cloud-init from configuring the network entirely?
No,

We have a case can explain this, one user has a vm image, which is configured with file /etc/udev/rules.d/70-persistent-net.rules linked to /dev/null, this is a normal operation. According to udev specifications, the user wants to disable this rule file. After creating an instance using this image, Cloudinit wrote to the udev file while configuring the network, but the file lined to /dev/null, and the permissions for the /dev/null were unexpectedly modified,(from 666 in most linux to 644), so we expect cloudinit to make check before configuring network write files to udev file,(Because this file is allowed to be linked to /dev/null according to the specification), Perhaps cloudinit can check if it is linked to /dev/null, if yes, unlink it before write.
Thanks