From df53ba67d00cba38f5ca4dea36a15921d5b69e14 Mon Sep 17 00:00:00 2001
From: Dimple Kuriakose <dimple.kuriakose@canonical.com>
Date: Thu, 9 Nov 2023 12:32:43 +0200
Subject: [PATCH] add azure explanation: Ubuntu on AKS worker nodes

---
 .wordlist.txt                                      |  2 +-
 .../confidential-computing.rst                     |  2 +-
 azure/azure-explanation/index.rst                  | 14 ++++++++++++++
 .../ubuntu-on-aks-worker-nodes.rst                 | 13 +++++++++++++
 .../understanding-ubuntu-on-azure.rst              |  2 +-
 azure/index.rst                                    |  3 +--
 6 files changed, 31 insertions(+), 5 deletions(-)
 rename azure/{ => azure-explanation}/confidential-computing.rst (98%)
 create mode 100644 azure/azure-explanation/index.rst
 create mode 100644 azure/azure-explanation/ubuntu-on-aks-worker-nodes.rst
 rename azure/{ => azure-explanation}/understanding-ubuntu-on-azure.rst (98%)

diff --git a/.wordlist.txt b/.wordlist.txt
index 0f7e54c7..e6c707ab 100644
--- a/.wordlist.txt
+++ b/.wordlist.txt
@@ -203,5 +203,5 @@ VMM
 EPYC
 virtualised
 CNCF
-
+AgentBaker
 
diff --git a/azure/confidential-computing.rst b/azure/azure-explanation/confidential-computing.rst
similarity index 98%
rename from azure/confidential-computing.rst
rename to azure/azure-explanation/confidential-computing.rst
index e425b45f..bfcbac0e 100644
--- a/azure/confidential-computing.rst
+++ b/azure/azure-explanation/confidential-computing.rst
@@ -1,7 +1,7 @@
 Confidential computing on Azure
 ===============================
 
-.. include:: ../reuse/common-intro.txt
+.. include:: ../../reuse/common-intro.txt
    :start-after: Start: Confidential computing
    :end-before: End: Confidential computing
 
diff --git a/azure/azure-explanation/index.rst b/azure/azure-explanation/index.rst
new file mode 100644
index 00000000..86adce19
--- /dev/null
+++ b/azure/azure-explanation/index.rst
@@ -0,0 +1,14 @@
+Explanation
+===========
+
+Discussion and clarification of some key topics:
+
+.. toctree::
+   :maxdepth: 1
+   
+   understanding-ubuntu-on-azure
+   ubuntu-on-aks-worker-nodes
+   confidential-computing
+   
+   
+   
\ No newline at end of file
diff --git a/azure/azure-explanation/ubuntu-on-aks-worker-nodes.rst b/azure/azure-explanation/ubuntu-on-aks-worker-nodes.rst
new file mode 100644
index 00000000..689efc56
--- /dev/null
+++ b/azure/azure-explanation/ubuntu-on-aks-worker-nodes.rst
@@ -0,0 +1,13 @@
+Ubuntu on AKS worker nodes
+==========================
+
+Azure Kubernetes Service (AKS) worker nodes use Ubuntu 22.04 LTS as their default operating system. The use of 22.04 LTS is recent. The earlier default was Ubuntu 18.04 LTS which is now out of standard support. So if you still run old AKS worker nodes with old versions of Kubernetes, you need to upgrade as Ubuntu 18.04 LTS no longer receives security fixes.
+
+The Ubuntu images used by the AKS worker nodes are not directly published by Canonical. They are published by the AKS team at Azure, after applying a configuration layer on a base image provided by Canonical. `AgentBaker`_ is the open source customisation tool used for doing this. Canonical works closely with the AKS team on this.
+
+.. important::
+
+    Unattended upgrades are disabled on AKS worker nodes. The service 'unattended-upgrades', that is used to automatically upgrade Ubuntu for security-related fixes, is disabled on AKS worker nodes.
+
+
+.. _`AgentBaker`: https://github.com/Azure/AgentBaker
diff --git a/azure/understanding-ubuntu-on-azure.rst b/azure/azure-explanation/understanding-ubuntu-on-azure.rst
similarity index 98%
rename from azure/understanding-ubuntu-on-azure.rst
rename to azure/azure-explanation/understanding-ubuntu-on-azure.rst
index f50e05bc..72582038 100644
--- a/azure/understanding-ubuntu-on-azure.rst
+++ b/azure/azure-explanation/understanding-ubuntu-on-azure.rst
@@ -4,7 +4,7 @@ Understanding Ubuntu on Azure
 Is Ubuntu available on Azure?
 -----------------------------
 
-Yes, all the supported versions of Ubuntu are available for free on Azure. See: :doc:`./azure-how-to/find-ubuntu-images`.
+Yes, all the supported versions of Ubuntu are available for free on Azure. See: :doc:`../azure-how-to/find-ubuntu-images`.
 
 ------------------------------------------------------
 Why are there multiple offers from Canonical on Azure?
diff --git a/azure/index.rst b/azure/index.rst
index 6d3af7fc..db61c306 100644
--- a/azure/index.rst
+++ b/azure/index.rst
@@ -55,8 +55,7 @@ contributions, suggestions, fixes and constructive feedback.
    :maxdepth: 2
 
    azure-how-to/index
-   understanding-ubuntu-on-azure
-   confidential-computing
+   azure-explanation/index
 
 .. _Code of conduct: https://ubuntu.com/community/ethos/code-of-conduct
 .. _Get support: https://ubuntu.com/cloud/public-cloud