cloud-init team mailing list archive

[James Falcon <james.falcon@xxxxxxxxxxxxx>]

This isn't documented. It's really not intended for users to be
overriding things defined in cloud.cfg, but it happens enough that we
should document it.

On your cloud instance, /etc/cloud/cloud.cfg (and anything in the .d
directory) specifies what cloud-init modules are run and in what stage
of cloud-init. More about stages and modules at:
https://cloudinit.readthedocs.io/en/latest/topics/boot.html
https://cloudinit.readthedocs.io/en/latest/topics/modules.html

The "once" in the example you listed is frequency. It specifies when a
module should be run. Some modules are run every single boot, some
only once per instance, and others only once ever. Valid frequencies
are "once", "once-per-instance", and "always". By default,
users-groups is run once per instance, so this is instructing
cloud-init to run this snippet only once. It's a way of using
cloud-init to get a key into the instance as a one-time thing.

On Tue, Sep 28, 2021 at 10:50 PM Yuri Kanivetsky
<yuri.kanivetsky@xxxxxxxxx> wrote:
>
> Hi,
>
> I've run into the following... what do you call it? piece of user data?
>
> Content-Type: multipart/mixed; boundary="//"
> MIME-Version: 1.0
>
> --//
> Content-Type: text/cloud-config; charset="us-ascii"
> MIME-Version: 1.0
> Content-Transfer-Encoding: 7bit
> Content-Disposition: attachment; filename="cloud-config.txt"
>
> #cloud-config
> cloud_final_modules:
> - [users-groups, once]
> users:
>   - name: username
>     ssh-authorized-keys:
>     - PublicKeypair
>
> https://aws.amazon.com/premiumsupport/knowledge-center/user-data-replace-key-pair-ec2/
>
> What is the syntax of cloud configs? The most unclear thing is once.
> Once per what? Is it documented? If I don't specify the
> cloud_final_modules key, does it change anything?
>
> Regards,
> Yuri
>
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