my cloud-init is not getting passed to instance

Question

I Am using ARM template to create a VM .

I have added the cloud-init data in CustomData variable filed and encoded with base64 , which is being passed to instance ,

                "customData": "[concat('#cloud-config\ntimezone: ', parameters('TimeZone'), '\nmanage_resolv_conf: true\nresolv_conf:\n  nameservers: [\"', parameters('DnsServers'), '\"]\nntp:\n  enabled: true\n  ntp_client: chrony\n  config:\n     confpath: /etc/chrony.conf\n     check_exe: chronyd\n     packages:\n       - chrony\n     service_name: chronyd\n     template: |\n         ## template:jinja\n         # My NTP Client config\n         {%- if servers %}# servers\n         {% endif %}\n         {% for server in servers -%}\n         server {{server}} iburst\n         {% endfor %}\n  servers: [', parameters('NtpServers'), ']\nusers:\n- name: insight\n  ssh_authorized_keys:\n  - ', parameters('InsightSshKey'),'\n- name: admin\n  ssh_authorized_keys:\n  - ', parameters('AdminSshKey'), '\n\nwrite_files:\n  - path: ', variables('configFile'),'\n    content: |\n', variables('appConfigFileContent'), '\n')]"
        },

passed to VM

              {
                        "type": "Microsoft.Compute/virtualMachines",
                        "apiVersion": "2019-12-01",
                        "name": "[variables('vmName')]",
                        "location": "[parameters('location')]",
                        "dependsOn": [
                                "[resourceId('Microsoft.Network/networkInterfaces', variables('networkInterfaceName'))]"
                        ],
                        "properties": {
                                "hardwareProfile": {
                                        "vmSize": "[parameters('vmSize')]"
                                },
                                "osProfile": {
                                        "computerName": "[variables('vmName')]",
                                        "adminUsername": "[variables('adminUsername')]",
                                        "customData": "[base64(variables('customData'))]",
                                        "linuxConfiguration": {
                                                "disablePasswordAuthentication": true,
                                                "ssh": {
                                                        "publicKeys": [{
                                                                "path": "[concat('/home/', variables('adminUsername'), '/.ssh/authorized_keys')]",
                                                                "keyData": "[parameters('AdminSshKey')]"
                                                        }]
                                                }
                                        }
                                },

cloud-init is failing in RHEL 8.9

in cloud-init error - isee

2024-03-18 14:39:44,177 - schema.py[WARNING]: Invalid cloud-config provided: Please run 'sudo cloud-init schema --system' to see the schema errors.

Cloud-init v. 23.1.1-11.el8_9.1 running 'modules:config' at Mon, 18 Mar 2024 14:39:44 +0000. Up 10693.83 seconds.

Cloud-init v. 23.1.1-11.el8_9.1 running 'modules:final' at Mon, 18 Mar 2024 14:39:45 +0000. Up 10694.47 seconds.

Cloud-init v. 23.1.1-11.el8_9.1 finished at Mon, 18 Mar 2024 14:39:45 +0000. Datasource DataSourceAzure [seed=IMDS]. Up 10694.67 seconds

[2024-03-18 14:39:45 root@Ribbon-RAMP-SA2: /home/admin ]# sudo cloud-init schema --system

Invalid cloud-config /var/lib/cloud/instances/70e4184e-9fb7-ed49-9238-cf864b50b577/cloud-config.txt

Error: Cloud config schema errors: format-l1.c1: File /var/lib/cloud/instances/70e4184e-9fb7-ed49-9238-cf864b50b577/cloud-config.txt needs to begin with "#cloud- config"

Error: Invalid cloud-config schema: user-data

once i run the suggested command from cloud-init , I see the file is empty

[2024-03-18 14:29:27 root@Ribbon-RAMP-SA2: /var/log ]# sudo cloud-init schema --system

Invalid cloud-config /var/lib/cloud/instances/70e4184e-9fb7-ed49-9238-cf864b50b577/cloud-config.txt

Error: Cloud config schema errors: format-l1.c1: File /var/lib/cloud/instances/70e4184e-9fb7-ed49-9238-cf864b50b577/cloud-config.txt needs to begin with "#cloud- config"

Error: Invalid cloud-config schema: user-data

Answer 1

@RAKESH B R Likely it is an issue with the format of the custom data. Is this working correctly when trying to deploy via Portal or CLI? It might be worth simplifying this by passing the cloud-init.txt directly using a method like this one.
https://www.atmosera.com/blog/arm-templates-and-cloud-init/

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