Customised machine: curtin_userdata script not executed as expected

[maasuser1]

As shown in the picture, the log looks weird, and the change has not been applied.

```yaml
#cloud-config
debconf_selections:
 maas: |
  {{for line in str(curtin_preseed).splitlines()}}
  {{line}}
  {{endfor}}

late_commands:
 maas: [wget, '--no-proxy', '{{node_disable_pxe_url}}', '--post-data', '{{node_disable_pxe_data}}', '-O', '/dev/null']
 10_motd_template: |
  curl 'URL to gist' -o /etc/motd
  sed -i "s/{hostname}/$(hostname)/g" /etc/motd
```

MAAS 3.4/Stable

Thanks!

[Anton Troyanov (troyanov)]

Hi maasuser1,

I am not super familiar with curtin, but I can see that all the commands [0] are passed as a list, not as a multiline string.

May I ask you to try representing your commands as a list instead?
Something like this or similar:

```
late_commands:
  10_motd_save : [curl, 'URL to gist','-o', '/etc/motd']
  10_motd_replace : [sed, '-i','"s/{hostname}/$(hostname)/g"', '/etc/motd']
```

[0]: https://curtin.readthedocs.io/en/latest/topics/config.html#stages

[maasuser1 (maasuser1)]

Thanks Anton. May I ask how to represent pipeline operators `>` `<` in the list?

[Anton Troyanov (troyanov)]

Hmm, I was wrong about list/multiline. This documentation [0] has several examples with a multiline string

```
debconf_selections:
  set1: |
   cloud-init cloud-init/datasources multiselect MAAS
   lxd lxd/bridge-name string lxdbr0
set2: lxd lxd/setup-bridge boolean true
```

[0]: https://readthedocs.org/projects/curtin/downloads/pdf/latest/

[Anton Troyanov (troyanov)]

maasuser1, may I ask you to try running your command defined as list?

[maasuser1 (maasuser1)]

I revised my command into one line:

```yaml
10_motd_template: [curl, '{redacted_url}', '-o', '/etc/motd']
```

```log
 Tue, 21 May. 2024 14:21:04 Node installation - 'curtin' running 'curl {redacted_url} -o /etc/motd'
```

The log shows above, but the `/etc/motd` file does not exist after deployed.

[Javier Fuentes (javier-fs)]

Hi maasuser1,

If you want to create and update a file during deployment with the purpose of using it later, you could directly use cloud-init syntax.

```
#cloud-config

runcmd:
  - [curl, "https://example.com/", --output, /etc/motd]
  - [sed, -i, -e, "s/Example/Test/g", /etc/motd]

```

If you would like to use the most recent version of the template, maybe `bootcmd` is a better fit. It is similar to `runcmd` but runs the commands in every boot.

Additionally, you could also download the template using `write_files`:
- https://curtin.readthedocs.io/en/latest/topics/config.html#write-files
- https://cloudinit.readthedocs.io/en/latest/reference/examples.html#writing-out-arbitrary-files
and modify it later with `bootcmd`.

[maasuser1 (maasuser1)]

Thank you Javier.

https://maas.io/docs/about-deploying-machines

According to the deployment process, cloud-init script must be uploaded during provisioning, but Curtin scripts will be populated by MAAS automatically.

[Javier Fuentes (javier-fs)]

I see your point.

If I understandand correctly:
- when you run a configuration you can deploy successfully a machine, i.e. the machine will end up in the "deployed" state
- the purpose of the configuration file is to download and customise a template file
- you would like that the customised template is available after the machine has been deployed
- the customised template is not used during the deployment process, but once the machine is deployed
- you are using the preseed files to create your own curtin configuration (https://maas.io/docs/how-to-customise-machines#pre-seed-cloud-init-2)
- you would like to use curtin so you do not have to upload the cloud-init configuration every time that you want to deploy a machine (https://maas.io/docs/how-to-customise-machines#pre-seed-cloud-init-2)

Correct me if any of my previous assumptions is wrong.

[maasuser1 (maasuser1)]

That's right!

I wanna set default settings like [SSH CA](https://www.lorier.net/docs/ssh-ca.html), MOTD (message of today), admin pubkey ...etc for all future deployed machines. Cloud-init requires manual involvement, while Curtin is finished in a one-go.

[Javier Fuentes (javier-fs)]

Could you try this config file (preseeds/curtin_userdata) and deploy a machine?

```
#cloud-config
debconf_selections:
  maas: |
    {{for line in str(curtin_preseed).splitlines()}}
    {{line}}
    {{endfor}}

late_commands:
  maas: [wget, '--no-proxy', '{{node_disable_pxe_url}}', '--post-data', '{{node_disable_pxe_data}}', '-O', '/dev/null']
  10_example_download: ['curtin', 'in-target', '--', 'wget', 'https://example.com/', '-O', '/etc/example.html']
  11_example_modify: ['curtin', 'in-target', '--', 'sed', '-i', '-e', 's/Example/Test/g', '/etc/example.html']
```

You should find the modified file (/etc/example.html) in the deployed machine.

If you want to add a customised configuration for your machine, you should let curtin know that the command will run in the target. Use "curtin in-target --" followed by the command that you want to run.

Additionally, something that can be useful is to use the endpoint `GET /MAAS/api/2.0/machines/{system_id}/op-get_curtin_config` to see the rendered curtin config file. That can help you to identify any problem during rendering.

[maasuser1 (maasuser1)]

Thank you, Javier, your script ran as expected. My mistake was that I didn't read the [manual](https://maas.io/docs/how-to-customise-machines) in detail.

Many thanks!

[maasuser1 (maasuser1)]

Template string does not work with Curtin:

```yaml
11_example_modify: ['curtin', 'in-target', '--', 'sed', '-i', '-e', 's/{hostname}/$(hostname)/g', '/etc/motd']
```

I eventually got "... $(hostname) ..." as a result, instead of "... MyMachine ...".