wip: adding instruction for kubeconfig and context

Author: manzil-infinity180

Kubeconfig.md

@@ -0,0 +1,190 @@
+## Kubeconfig
+
+kubectl uses one file which is kubeconfig to authenticate itself 
+
+if client want then it need private key and client certificate 
+
+## How to access the kubeconfig file on our machine 
+
+```bash
+rahulxf@Rahuls-MacBook-Air-3 ~ % cd $HOME/.kube/  
+
+rahulxf@Rahuls-MacBook-Air-3 .kube % ls -l
+total 160
+drwxr-x---@ 4 rahulxf  staff    128 Jan 17 22:46 cache
+-rw-------@ 1 rahulxf  staff  31948 Feb 17 10:48 config
+-rw-r--r--  1 rahulxf  staff   7973 Feb  4 16:01 karmada-apiserver.config
+-rw-------  1 rahulxf  staff  13415 Feb 11 19:28 karmada.config
+-rw-r--r--  1 rahulxf  staff      4 Feb 17 10:43 kubectx
+drwxr-xr-x  4 rahulxf  staff    128 Feb 17 10:48 kubens
+-rw-r--r--  1 rahulxf  staff  16652 Feb  2 22:01 members.config
+
+rahulxf@Rahuls-MacBook-Air-3 .kube %
+
+rahulxf@Rahuls-MacBook-Air-3 .kube % vim config
+rahulxf@Rahuls-MacBook-Air-3 .kube % vim config
+```
+
+* config is the kubeconfig file 
+
+```
+apiVersion: v1
+clusters:
+- cluster:
+certificate-authority-data: LS0tLS1CRUdJTiBDRVJUSUZJQ0FURS0tLS0tCk1JSURQRENDQWlTZ0F3SUJBZ0lDQm5Zd0RRWUpLb1pJa......
+server: https://cp1.localtest.me:9443
+
+name: cp1-cluster
+- cluster:
+server: ""
+
+name: its1
+- cluster:
+certificate-authority-data: LS0tLS1CRUdJTiBDRVJUSUZJQ0FURS0tLS0tCk1JSUJlRENDQVIyZ0F3SUJBZ0lCQURBS0JnZ3Foa2pPU....
+server: https://its1.localtest.me:9443
+name: its1-cluster
+
+contexts:
+- context:
+cluster: kind-cluster1
+user: kind-cluster1
+name: cluster1
+
+- context:
+cluster: kind-cluster2
+user: kind-cluster2
+name: cluster2
+
+users:
+- name: cp1-admin
+user:
+client-certificate-data: LS0tLS1CRUdJTiBDRVJUSUZJQ0FURS0tLS0tCk1JSURSVENDQWkyZ0F3SUJBZ0lDQm5vd0RRWUpLb1pJaHZjTkFRRUxCUUF3UHpFVE1CRUdBMVVFQ2hNS1MzVmkKWlhKdVpYUmxjekVUTUJFR0ExVUVDeE1LUVZCSklGTmxjblpsY2pFVE1CRUdBMVVFQXhNS2EzVmlaWEp1WlhSbApjekFlRncweU5UQXhNVGN4TmpJek5UUmFGdzB6TlRB
+
+client-key-data: LS0tLS1CRUdJTiBSU0EgUFJJVkFURSBLRVktLS0tLQpNSUlFcGdJQkFBS0NBUUVBM1l0MmgzVHp6NHgzYnU2akhJWXVDZHVKbWpTejNrSWtYVFczNEFHN2ZtR2hENS9DCjZNOFdtZGd1clFjU0doQVIyOENSaUhKUHoxckU4
+
+- name: its1-admin
+
+user:
+
+client-certificate-data: LS0tLS1CRUdJTiBDRVJUSUZJQ0FURS0tLS0tCk1JSUJrRENDQVRlZ0F3SUJBZ0lJVmloSTBuYzg0dDR3Q2dZS
+
+client-key-data: LS0tLS1CRUdJTiBFQyBQUklWQVRFIEtFWS0tNNDkKQXdFSG9VUURRZ0FFa1ZXYWNmbmwyTlg0L1d6NCthVS9JVzVyU05lSVhGZW5ROT
+
+- name: kind-cluster1
+
+user:
+client-certificate-data: LS0tLS1CRUdJTiBDRVJUSUZJQ0FURS0tLS0tCk1JSURLVENDQWhHZ0F3SUJBZ0lJR0ZhWGh1RFU4c2t3RFFZSktvWklW9
+
+client-key-data: LS0tLS
+```
+
+How to add users 
+
+```
+$ kubectl config set-credentials devuser --client-certificate du.crt --client-key du.key
+
+User "devuser" set.
+```
+
+You also need to map it , i mean you need to add context for this user for the cluster 
+
+```
+$ kubectl config set-context --cluster kind-kind --user devuser
+
+Context "devuser-kind" created
+```
+
+```
+- context:
+	cluster: kind-kind
+	user: devuser
+  name: devuser-kind
+```
+
+If you want to check which context we are using 
+
+`$ kubectl config current-context`
+
+or 
+you can install `kubectx` 
+
+* Flow of kubectl for looking kubeconfig file 
+  1) --kubeconfig flag to kubectl command
+  2) Then it will look for the environmental variable (env)
+  3) after in the last it will look for the $HOME/.kube/config file 
+
+Suppose you want - 2,3 kubeconfig file as one file then you can do this like you can specify the kubeconfig file with colon(:) separated 
+
+```
+$ export KUBECONFIG=~/.kube/config:~/.kube/karmada.config:~/.kube/karmada-apiserver.config
+```
+
+<img width="1120" alt="Screenshot 2025-02-18 at 11 21 48 PM" src="https://github.com/user-attachments/assets/d1d742bf-d308-42a8-bcf6-41b4d5c881da" />
+
+To authenticate the user to kubernetes cluster we will do client certificate management 
+
+docker ps  (get the id )
+docker exec -it <id> bash
+cd /etc/kubernetes/pki 
+ls -l (you will see the key, csr and other files )
+
+
+* So for creating private key and csr key you can run this command to generate
+
+<img width="1179" alt="shapes at 25-02-20 00 13 41" src="https://github.com/user-attachments/assets/2aedf2d0-8b1b-4a23-9ce0-c815020ec5fa" />
+
+Generate new ssl key:
+-----
+
+```
+$ openssl genrsa -out rahulxf.key 2048
+```
+
+Generate new certificate signing request for the issuer authority:
+----
+
+```
+#CN is the name of the user
+#O is the group name. When you will create the rolebinding do the binding based on group name. 
+$ openssl req -new -key rahulxf.key -out rahulxf.csr -subj "/CN=rahulxf/0=developers"
+```
+
+<img width="1157" alt="Screenshot 2025-02-19 at 12 46 29 AM" src="https://github.com/user-attachments/assets/c3cf391d-1a0a-4c4d-867f-da607225247f" />
+
+<img width="986" alt="Screenshot 2025-02-19 at 12 56 19 AM" src="https://github.com/user-attachments/assets/850c5a52-7c21-44b0-89cc-1ce229dca0cd" />
+
+The next step is to creating the user and setting up the context between the user and cluster in kubeconfig file 
+------
+
+```
+# Adding user 
+$ kubectl config set-credentials rahulxf --client-certificate rahulxf.crt --client-key rahulxf.key
+
+# Creating context for the user and cluster
+$ kubectl config set-context rahulxf-kind --user rahulxf --cluster kind-cluster2
+
+```
+<img width="937" alt="Screenshot 2025-02-20 at 12 17 04 AM" src="https://github.com/user-attachments/assets/6b653c3b-49e8-48f4-add9-9859023d9fe8" />
+
+* Here you can look for the kubeconfig file 
+
+<img width="1499" alt="Screenshot 2025-02-19 at 1 09 37 AM" src="https://github.com/user-attachments/assets/367eda1b-0ae6-4604-a2e7-62793769e42a" />
+
+* see your context using command
+
+```
+$ kubectl config current-context
+$ kubectl config get-contexts
+$ kubectl config use-context <context_name>
+
+# OR use kubectx
+$ kubectx
+```
+<img width="1094" alt="Screenshot 2025-02-19 at 1 10 23 AM" src="https://github.com/user-attachments/assets/093537f4-76b7-4f11-890e-77781eefa5cd" />
+
+* allow namespaces 
+<img width="1310" alt="Screenshot 2025-02-19 at 1 17 41 AM" src="https://github.com/user-attachments/assets/b9e2ca7c-ac1c-4b7c-9384-4ec96a951f15" />
+
+
+* allow pods 
+<img width="1310" alt="Screenshot 2025-02-19 at 1 23 04 AM" src="https://github.com/user-attachments/assets/9967a9df-bac0-42d9-9b3a-d177e764b2b5" />