yahoo-eng-team team mailing list archive

[Peter Surda <2011298@xxxxxxxxxxxxxxxxxx>]

Public bug reported:

This isn't really a bug, it's more of a missing functionality.

The quick description is that if you specify the network configuration
by a kernel command line parameter (`ip=blahblahblah`), there doesn't
appear to be a way to override it by defining a different network setup
in cloud-init. The kernel command line will always take precedence no
matter what you define in `meta-data` or `user-data`.

This is the conclusion I drew both from the documentation, as well as by
looking at the source on GitHub. The kernel command line has absolute
priority and can't be overriden. I found a workaround, by writing the
config file (`/etc/netplan/50-cloud-init.yml` in my case) directly
through "write_files" and then executing "netplan apply" in "runcmd".
This does what I want, but it doesn't look nice.

Perhaps you're wondering why I need this. I boot ubuntu MAAS images over
network. In some data centers DHCP isn't available and at the same time
I need to assign more than one IP address to the system, and/or
configure bonding. So the bootloader constructs the kernel command line,
the machine boots, but only has one ethernet interface configured, with
one IP address. I can't remove the kernel command line argument, as then
cloud-init doesn't know how to configure the network in order to
download the `user-data` / `meta-data`.

Please consider providing an alternative approach to the workaround I
explained above.

** Affects: cloud-init
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/2011298

Title:
  network config can't override kernel command line arguments

Status in cloud-init:
  New

Bug description:
  This isn't really a bug, it's more of a missing functionality.

  The quick description is that if you specify the network configuration
  by a kernel command line parameter (`ip=blahblahblah`), there doesn't
  appear to be a way to override it by defining a different network
  setup in cloud-init. The kernel command line will always take
  precedence no matter what you define in `meta-data` or `user-data`.

  This is the conclusion I drew both from the documentation, as well as
  by looking at the source on GitHub. The kernel command line has
  absolute priority and can't be overriden. I found a workaround, by
  writing the config file (`/etc/netplan/50-cloud-init.yml` in my case)
  directly through "write_files" and then executing "netplan apply" in
  "runcmd". This does what I want, but it doesn't look nice.

  Perhaps you're wondering why I need this. I boot ubuntu MAAS images
  over network. In some data centers DHCP isn't available and at the
  same time I need to assign more than one IP address to the system,
  and/or configure bonding. So the bootloader constructs the kernel
  command line, the machine boots, but only has one ethernet interface
  configured, with one IP address. I can't remove the kernel command
  line argument, as then cloud-init doesn't know how to configure the
  network in order to download the `user-data` / `meta-data`.

  Please consider providing an alternative approach to the workaround I
  explained above.

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