Merge pull request #232652 from divargas-msft/patch-5

[Doc-a-thon] Updating cloud-init-deep-dive

Author: Stacyrch140

articles/virtual-machines/linux/cloud-init-deep-dive.md

@@ -4,50 +4,50 @@ description: Deep dive for understanding provisioning an Azure VM using cloud-in
 author: mattmcinnes 
 ms.service: virtual-machines
 ms.topic: conceptual
-ms.date: 07/06/2020
+ms.date: 03/29/2023
 ms.author: mattmcinnes
 ms.reviewer: cynthn
 ms.subservice: cloud-init
 ---
 
 # Diving deeper into cloud-init
 
-**Applies to:** :heavy_check_mark: Linux VMs :heavy_check_mark: Flexible scale sets 
+**Applies to:** :heavy_check_mark: Linux VMs :heavy_check_mark: Flexible scale sets
 
 To learn more about [cloud-init](https://cloudinit.readthedocs.io/en/latest/index.html) or troubleshoot it at a deeper level, you need to understand how it works. This document highlights the important parts, and explains the Azure specifics.
 
-When cloud-init is included in a generalized image, and a VM is created from that image, it will process configurations and run through 5 stages during the initial boot. These stages matter, as it shows you at what point cloud-init will apply configurations. 
-
+When cloud-init is included in a generalized image, and a VM is created from that image, it processes configurations and run-through five stages during the initial boot. These stages matter, as it shows you at what point cloud-init applies configurations.
 
 ## Understand Cloud-Init configuration
-Configuring a VM to run on a platform, means cloud-init needs to apply multiple configurations, as an image consumer, the main configurations you will be interacting with is `User data` (customData), which supports multiple formats. For more information, see [User-Data Formats & cloud-init 21.2 documentation](https://cloudinit.readthedocs.io/en/latest/topics/format.html#user-data-formats). You also have the ability to add and run scripts (/var/lib/cloud/scripts) for additional configuration, below discusses this in more detail.
+
+Configuring a VM to run on a platform, means cloud-init needs to apply multiple configurations, as an image consumer, the main configurations you interact with is `User data` (customData), which supports multiple formats. For more information, see [User-Data Formats & cloud-init 21.2 documentation](https://cloudinit.readthedocs.io/en/latest/topics/format.html#user-data-formats). You also have the ability to add and run scripts (/var/lib/cloud/scripts) for other configuration.
 
 Some configurations are already baked into Azure Marketplace images that come with cloud-init, such as:
 
-1. **Cloud data source** - cloud-init contains code that can interact with cloud platforms, these are called 'datasources'. When a VM is created from a cloud-init image in [Azure](https://cloudinit.readthedocs.io/en/latest/reference/datasources/azure.html#azure), cloud-init loads the Azure datasource, which will interact with the Azure metadata endpoints to get the VM specific configuration.
-2. **Runtime config** (/run/cloud-init)
-3. **Image config** (/etc/cloud), like `/etc/cloud/cloud.cfg`, `/etc/cloud/cloud.cfg.d/*.cfg`. An example of where this is used in Azure, it is common for the Linux OS images with cloud-init to have an Azure datasource directive, that tells cloud-init what datasource it should use, this saves cloud-init time:
+* **Cloud data source** - cloud-init contains code that can interact with cloud platforms, these codes are called 'datasources'. When a VM is created from a cloud-init image in [Azure](https://cloudinit.readthedocs.io/en/latest/reference/datasources/azure.html#azure), cloud-init loads the Azure datasource, which interacts with the Azure metadata endpoints to get the VM specific configuration.
+* **Runtime config** (/run/cloud-init).
+* **Image config** (/etc/cloud), like `/etc/cloud/cloud.cfg`, `/etc/cloud/cloud.cfg.d/*.cfg`. An example of where this configuration is used in Azure, it's common for the Linux OS images with cloud-init to have an Azure datasource directive that tells cloud-init what datasource it should use, this configuration saves cloud-init time:
 
    ```bash
-   /etc/cloud/cloud.cfg.d# cat 90_dpkg.cfg
+   sudo cat /etc/cloud/cloud.cfg.d/90_dpkg.cfg
+   ```
+
+   ```output
    # to update this file, run dpkg-reconfigure cloud-init
    datasource_list: [ Azure ]
    ```
 
-
 ## Cloud-init boot stages (processing configuration)
 
-When provisioning with cloud-init, there are 5 stages of boot, which process configuration, and shown in the logs.
-
-1. [Generator Stage](https://cloudinit.readthedocs.io/en/latest/topics/boot.html#generator): The cloud-init systemd generator starts, and determines that cloud-init should be included in the boot goals, and if so, it enables cloud-init. 
+When you are provisioning VMs with cloud-init, there are five stages of boot, which process configuration, and shown in the logs.
 
-2. [Cloud-init Local Stage](https://cloudinit.readthedocs.io/en/latest/topics/boot.html#local): Here cloud-init will look for the local "Azure" datasource, which will enable cloud-init to interface with Azure, and apply a networking configuration, including fallback.
+1. [Generator Stage](https://cloudinit.readthedocs.io/en/latest/topics/boot.html#generator): The cloud-init systemd generator starts, and determines that cloud-init should be included in the boot goals, and if so, it enables cloud-init.
+2. [Cloud-init Local Stage](https://cloudinit.readthedocs.io/en/latest/topics/boot.html#local): Here cloud-init looks for the local "Azure" datasource, which enables cloud-init to interface with Azure, and apply a networking configuration, including fallback.
+3. [Cloud-init init Stage (Network)](https://cloudinit.readthedocs.io/en/latest/topics/boot.html#network): Networking should be online, and the NIC and route table information should be generated. At this stage, the modules listed in `cloud_init_modules` in `/etc/cloud/cloud.cfg` runs. The VM in Azure is mounted, the ephemeral disk is formatted, the hostname is set, along with other tasks.
 
-3. [Cloud-init init Stage (Network)](https://cloudinit.readthedocs.io/en/latest/topics/boot.html#network): Networking should be online, and the NIC and route table information should be generated. At this stage, the modules listed in `cloud_init_modules` in /etc/cloud/cloud.cfg will be run. The VM in Azure will be mounted, the ephemeral disk is formatted, the hostname is set, along with other tasks.
+   The following are some of the `cloud_init_modules`:
 
-   These are some of the `cloud_init_modules`:
-   
-   ```bash
+   ```config
    - migrator
    - seed_random
    - bootcmd
@@ -60,18 +60,16 @@ When provisioning with cloud-init, there are 5 stages of boot, which process con
    - update_hostname
    - ssh
    ```
-   
-   After this stage, cloud-init will signal to the Azure platform that the VM has been provisioned successfully. Some modules may have failed, not all module failures will result in a provisioning failure.
-
-4. [Cloud-init Config Stage](https://cloudinit.readthedocs.io/en/latest/topics/boot.html#config): At this stage, the modules in `cloud_config_modules` defined and listed in /etc/cloud/cloud.cfg will be run.
 
+   After this stage, cloud-init sends a signal to the Azure platform that the VM has been provisioned successfully. Some modules may have failed, not all module failures result in a provisioning failure.
 
-5. [Cloud-init Final Stage](https://cloudinit.readthedocs.io/en/latest/topics/boot.html#final): At this final stage, the modules in `cloud_final_modules`, listed in /etc/cloud/cloud.cfg, will be run. Here modules that need to be run late in the boot process run, such as package installations and run scripts etc. 
+4. [Cloud-init Config Stage](https://cloudinit.readthedocs.io/en/latest/topics/boot.html#config): At this stage, the modules in `cloud_config_modules` defined and listed in `/etc/cloud/cloud`.cfg runs.
+5. [Cloud-init Final Stage](https://cloudinit.readthedocs.io/en/latest/topics/boot.html#final): At this final stage, the modules in `cloud_final_modules`, listed in `/etc/cloud/cloud.cfg`, runs. Here modules that need to be run late in the boot process run, such as package installations and run scripts etc.
 
-   -   During this stage, you can run scripts by placing them in the directories under `/var/lib/cloud/scripts`:
-   - `per-boot` - scripts within this directory, run on every reboot
-   - `per-instance` - scripts within this directory run when a new instance is first booted
-   - `per-once` - scripts within this directory run only once
+   - During this stage, you can run scripts by placing them in the directories under `/var/lib/cloud/scripts`:
+     - `per-boot` - scripts within this directory, run on every reboot
+     - `per-instance` - scripts within this directory run when a new instance is first booted
+     - `per-once` - scripts within this directory run only once
 
 ## Next steps