2021-03-18-kubernetes-retrieve-container-image-inventory.md

Author: NetoTrest

_posts/kubernetes/2021-03-18-kubernetes-retrieve-container-image-inventory.md

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+---
+title: kubernetes >  retrieve container image inventory
+categories: kubernetes
+---
+We would be using kubectl and then write some Python code to retrieve the list of images of containers 
+running in a GKE Kubernetes cluster. Some familiarity with YAML, Python, Kubectl and fundamentals of 
+Kubernetes would be essential to understand the post better.
+
+# Details of Pods
+Lets view the list pods in all namespaces.
+```
+$ kubectl get po -A
+NAMESPACE     NAME                                                        READY   STATUS    RESTARTS   AGE
+kube-system   event-exporter-gke-564fb97f9-6bt5p                          2/2     Running   1          13m
+kube-system   fluentbit-gke-2mfvq                                         2/2     Running   0          13m
+kube-system   fluentbit-gke-s5cjj                                         2/2     Running   0          13m
+---TRUNCATED--
+```
+
+We can get more information about the pods by viewing their details in yaml format.
+```
+$ kubectl get po -A -o yaml
+apiVersion: v1
+items:
+- apiVersion: v1
+  kind: Pod
+  metadata:
+    annotations:
+      components.gke.io/component-name: event-exporter
+      components.gke.io/component-version: 1.0.9
+    creationTimestamp: "2021-03-18T11:33:52Z"
+    generateName: event-exporter-gke-564fb97f9-
+---TRUNCATED---
+```
+
+Let's save this info in a file.
+```
+$ kubectl get po -A -o yaml > /tmp/details-of-pods.yaml
+
+$ cat /tmp/details-of-pods.yaml 
+apiVersion: v1
+items:
+- apiVersion: v1
+  kind: Pod
+  metadata:
+    annotations:
+      components.gke.io/component-name: event-exporter
+      components.gke.io/component-version: 1.0.9
+    creationTimestamp: "2021-03-18T11:33:52Z"
+    generateName: event-exporter-gke-564fb97f9-
+---TRUNCATED---
+```
+
+# Retrive the images
+Since we have the required data in a file, we can parse it to retrieve the info we need, in this case 
+the image of containers.
+
+Let's get into Python shell, and import the yaml package, that helps us parsing YAML content.
+```
+$ python3
+Python 3.8.5 (default, Jan 27 2021, 15:41:15) 
+[GCC 9.3.0] on linux
+Type "help", "copyright", "credits" or "license" for more information.
+>>> import yaml
+```
+
+We are now to going to read the file and create a new object that stores the YAML content as a 
+dictionary object.
+```
+with open('/tmp/details-of-pods.yaml') as f:
+    pod_list = yaml.load(f, Loader=yaml.FullLoader)
+    print(type(pod_list))  
+    # should print <class 'dict'>
+```
+
+What we now have is a dictionary object and we should be able to parse it using standard dictionary 
+methods available in Python.
+```
+for key in pod_list:
+    print(key)
+    # should print
+    ```
+    apiVersion
+    items
+    kind
+    metadata
+    ```
+```
+
+There are 4 main keys in the dictionary, and we are interested in items, as that refers to the list of 
+Pods. We can iterate over the items list, and each item would be a dictionary again as that refers to 
+one complete Pod manifest.
+
+Let's create a file, where we can store the results, we are retreiving.
+```
+file = open('/tmp/container-img-inventory.csv', 'w')
+file.write('Pod Name\tPod Namespace\tContainer Name\tContainer Image\n')
+```
+Note that \t referes to tab \n refers to newline character.
+
+```
+for item in pod_list['items']:
+    print(item.keys())
+    # should print
+    ```
+    dict_keys(['apiVersion', 'kind', 'metadata', 'spec', 'status'])
+    dict_keys(['apiVersion', 'kind', 'metadata', 'spec', 'status'])
+    --TRUNCATED
+    ```
+```
+
+In a Pod manifest, its name would be present in metadata.name, its namespace would be present in 
+metadata.namespace, the spec of its containers would be present in spec.containers. Let's check a 
+sample Pod manifest for clarity.
+```
+apiVersion: v1
+  kind: Pod
+  metadata:
+    ---TRUNCATED---
+    name: event-exporter-gke-564fb97f9-6bt5p
+    namespace: kube-system
+    --TRUNCATED---
+  spec:
+    containers:
+    - image: gke.gcr.io/prometheus-to-sd:v0.10.0-gke.0
+      name: prometheus-to-sd-exporter
+      ---TRUNCATED---
+  status:
+    ---TRUNCATED---
+```
+
+Note that spec.containers is a List and each list item i.e. container would have a name and image. 
+So the mapping for those names and images in our Pod manifest would be spec.containers[].name and 
+spec.containers[].image respectively.
+
+We are now going to get the details discussed above for each Pod.
+
+```
+for item in pod_list['items']:
+    print(item.keys())
+    pod_name = item['metadata']['name']
+    pod_namespace = item['metadata']['namespace']
+    container_list = item['spec']['containers']
+    for container in container_list:
+        container_name = container['name']
+        container_image = container['image']
+        file.write(f'{pod_name}\t{pod_namespace}\t{container_name}\t{container_image}\n')
+```
+
+The file should contain the details that we need.
+```
+$ head /tmp/container-img-inventory.csv 
+Pod Name	Pod Namespace	Container Name	Container Image
+event-exporter-gke-564fb97f9-6bt5p	kube-system	event-exporter	gke.gcr.io/event-exporter:v0.3.4-gke.0
+event-exporter-gke-564fb97f9-6bt5p	kube-system	prometheus-to-sd-exporter	gke.gcr.io/prometheus-to-sd:v0.10.0-gke.0
+fluentbit-gke-2mfvq	kube-system	fluentbit	gke.gcr.io/fluent-bit:v1.3.11-gke.0
+fluentbit-gke-2mfvq	kube-system	fluentbit-gke	gke.gcr.io/fluent-bit-gke-exporter:v0.11.4-gke.0
+fluentbit-gke-s5cjj	kube-system	fluentbit	gke.gcr.io/fluent-bit:v1.3.11-gke.0
+fluentbit-gke-s5cjj	kube-system	fluentbit-gke	gke.gcr.io/fluent-bit-gke-exporter:v0.11.4-gke.0
+fluentbit-gke-xxpgg	kube-system	fluentbit	gke.gcr.io/fluent-bit:v1.3.11-gke.0
+fluentbit-gke-xxpgg	kube-system	fluentbit-gke	gke.gcr.io/fluent-bit-gke-exporter:v0.11.4-gke.0
+gke-metrics-agent-9q24j	kube-system	gke-metrics-agent	gke.gcr.io/gke-metrics-agent:0.2.1-gke.0
+```
+
+Since the file is in csv format, we could use utilities like Excel or Google sheets to view the 
+content in a graphical way.
+
+---end-of-post---
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