userless conf fails assign user[0] as the default user

[ubuntu-server-builder]

This bug was originally filed in Launchpad as LP: #1041384

Launchpad details

affected_projects = []
assignee = None
assignee_name = None
date_closed = 2012-09-19T21:08:58.585528+00:00
date_created = 2012-08-24T21:43:13.622929+00:00
date_fix_committed = 2012-09-19T21:08:58.585528+00:00
date_fix_released = 2012-09-19T21:08:58.585528+00:00
id = 1041384
importance = high
is_complete = True
lp_url = https://bugs.launchpad.net/cloud-init/+bug/1041384
milestone = None
owner = darkmuggle-deactivatedaccount
owner_name = Ben Howard
private = False
status = fix_released
submitter = darkmuggle-deactivatedaccount
submitter_name = Ben Howard
tags = []
duplicates = []

Launchpad user Ben Howard(darkmuggle-deactivatedaccount) wrote on 2012-08-24T21:43:13.622929+00:00

The userles merge fails to properly assign user[0] as the default user due to default configuration and the way that cloud-init merges the ondisk configuration with the cloud-config sent by the user.

cloud-init/config/cloud.cfg (Default configuration)
  4 # Implement for Ubuntu only: create the default 'ubuntu' user
  5 users:
  6 default: true
  7

If a user launches with the cloud config of:
users:
    foo: True

The expected behavior is that user foo would be configured equivalent to the parameter "user: foo".

However, due to this code and the default configuration:
cloud-init/cloudinit/stages.py
164
165.....def _read_cfg(self, extra_fns):
166.........no_cfg_paths = helpers.Paths({}, self.datasource)
167.........merger = helpers.ConfigMerger(paths=no_cfg_paths,
168.......................................datasource=self.datasource,
169.......................................additional_fns=extra_fns,
170.......................................base_cfg=self._read_base_cfg())
171........return merger.cfg

cloud-init generates the user lists as:
users:
    default: True
    foo: True

So what is happening is the default configuratoin is merged with the cloud-config.

Effectively this means that regardless of the user configuration send in the cloud-config:
  - The ubuntu user will always be created on a Ubuntu systems
  - The ubuntu user is always user[0]
  - Any configured user is user[n+1], and therefore will not be uzer[0]
  - A cloud-config of "user: default: false" will be ignored.

IMHO, this is a pretty serious bug.

[ubuntu-server-builder]

Launchpad user Ben Howard(darkmuggle-deactivatedaccount) wrote on 2012-08-24T22:17:57.644633+00:00

Filed MP: #121295 as a potential fix.

[ubuntu-server-builder]

Launchpad user Ben Howard(darkmuggle-deactivatedaccount) wrote on 2012-08-24T22:20:23.038973+00:00

Note, this bug appears to affect other cloud-config options that have a default option set.

[ubuntu-server-builder]

Launchpad user Scott Moser(smoser) wrote on 2012-08-27T13:24:53.928691+00:00

What you're running into is really just a generic limitation of the merge routine that cloud-init uses. We had hoped to improve the function of this merge routine at Bug 1023179, but have not implemented this yet.

I don't think its really safe or desirable to change this at the moment.

A more reasonable change I think is to change the users and groups to be lists of dicts rather than a dict of dicts.
dicts get added to or updated, but lists get replaced. So, if your default config entry is a list rather than a dict, then the user's value will entirely replace the list.

Ie:
groups:

• ubuntu: [foo,bar]
• cloud-users
  users:
• name: ubuntu

you could also allow for the case where an entry in the ''users" list is a string:
users:

• default

basically, then the presense of the 'default' user in the users list would trigger creation of the "default" user.

[ubuntu-server-builder]

Launchpad user Ben Howard(darkmuggle-deactivatedaccount) wrote on 2012-09-19T21:08:52.555574+00:00

This was fixed in r641. Marking as fixed released.