# Kubernetes Administration 101: Basic Cluster Tasks Every Admin Should Know

## **Examining pods**

Using `kubectl` we can examine the pods running in the cluster. The simplest way is to run this command.

```bash
# Simple command to examine the pods
$ kubectl get po

# To get information about the pods running in a specific namespace and showing their IP addresses
# in this example the kube-system namespace
$ kubectl get po -n kube-system -o wide
```

By using the `-o wide` option we can get additional information, including a column specifying the IP addresses.

## **Performing a backup of etcd**

The datastore etcd, also known as the cluster store, has all the stateful configuration information about our cluster. One common operation is to back up the etcd datastore using a CLI utility called `etcdctl`.

### **Pre-requisite**

* Have `etcdctl` installed
    

```bash
$ sudo apt update; apt install -y etcd-client
# Following that we can perform a snapshot backup of the etcd datastore
$ etcdctl snapshot save snapshotdb --cacert /etc/kubernetes/pki/etcd/ca.crt --cert /etc/kubernetes/pki/etcd/server.crt --key /etc/kubernetes/pki/server.key
# ... output omitted
Snapshot saved at snapshotdb
```

The above command creates a snapshot in the current directory called `snapshotdb`. To check the status of the snapshot you can use `$ etcdctl snapshot status snapshotdb --write-out=table`. This will generate a table like below

```bash
+----------+----------+------------+------------+
|   HASH   | REVISION | TOTAL KEYS | TOTAL SIZE |
+----------+----------+------------+------------+
| e4f4157c |   102366 |        817 |     2.2 MB |
+----------+----------+------------+------------+
```

## **Restoring etcd from snapshot**

If needed, we can use etcdctl to also restore the backed up version of the datastore. In order to perform the restore operation, we need to specify a directory already accessed by etcd. By checking the `etcd.yaml` file in the `/etc/kubernetes/manifests` directory, we can change that directory to something like `/var/lib/etcd-restore`.

```bash
$ etcdctl snapshot restore <snapshot-name> --data-dir /var/lib/etcd-restore
```

## **Upgrading Kubernetes version**

The last task we will perform in this lab is upgrading the version of `kubeadm`. For example, if in the exam there's a question about a company needing to upgrade the Kubernetes controller to version X, then we know that `kubeadm` is the tool to use. The first thing to do is to view the version of our control plane components.

```bash
# This will show a list of control plane components and their current version
# as well as the version to which we can upgrade
$ kubeadm upgrade plan

COMPONENT                 NODE                      CURRENT    TARGET
kube-apiserver            acing-cka-control-plane   v1.32.2    v1.32.3
kube-controller-manager   acing-cka-control-plane   v1.32.2    v1.32.3
kube-scheduler            acing-cka-control-plane   v1.32.2    v1.32.3
kube-proxy                                          1.32.2     v1.32.3
CoreDNS                                             v1.11.3    v1.11.3
etcd                      acing-cka-control-plane   3.5.16-0   3.5.16-0
```

After running the command above you will get the command needed to upgrade, as output. `$ kubeadm upgrade apply v1.32.3`