I recently discovered nushell. It is similar to shells like bash and zsh, but every command works on structured data. Here are some examples of how you can use nushell with kubectl to explore your kubernetes cluster more ergonomically.
kubectl get pods
“Normal” kubectl get pods looks like this.
kubectl get pods
NAME READY STATUS RESTARTS AGE
grafana-alloy-tqb7l 2/2 Running 0 2d14h
grafana-alloy-tlwm9 2/2 Running 0 2d14h
prometheus-server-659b75c446-nzxbp 0/2 ContainerCreating 0 10h
grafana-79c45cd5f9-jpr6k 0/1 Init:0/1 0 10h
grafana-alloy-tlrvl 2/2 Running 6 (68m ago) 2d14h
kube-state-metrics-6965d77b4-jzvlb 1/1 Running 3 (68m ago) 2d14h
grafana-alloy-97c8n 2/2 Running 6 (68m ago) 2d14h
You can use nushell to parse this data into a tabular format. The trick is to have kubectl respond with json, and then use nushell to parse the json.
kubectl get pods -o json | from json
╭────────────┬──────────────────╮
│ apiVersion │ v1 │
│ items │ [table 20 rows] │
│ kind │ List │
│ metadata │ {record 1 field} │
╰────────────┴──────────────────╯
From there, you can build more complex queries.
kubectl get pods -o json | from json | get items | flatten | select apiVersion kind name namespace creationTimestamp
╭───┬────────────┬──────┬────────────────────────────────────┬────────────┬──────────────────────╮
│ # │ apiVersion │ kind │ name │ namespace │ creationTimestamp │
├───┼────────────┼──────┼────────────────────────────────────┼────────────┼──────────────────────┤
│ 0 │ v1 │ Pod │ grafana-alloy-tqb7l │ monitoring │ 2024-07-12T01:49:46Z │
│ 1 │ v1 │ Pod │ grafana-alloy-tlwm9 │ monitoring │ 2024-07-12T01:49:46Z │
│ 2 │ v1 │ Pod │ prometheus-server-659b75c446-nzxbp │ monitoring │ 2024-07-14T06:24:25Z │
│ 3 │ v1 │ Pod │ grafana-79c45cd5f9-jpr6k │ monitoring │ 2024-07-14T06:24:25Z │
│ 4 │ v1 │ Pod │ grafana-alloy-tlrvl │ monitoring │ 2024-07-12T01:49:46Z │
│ 5 │ v1 │ Pod │ kube-state-metrics-6965d77b4-jzvlb │ monitoring │ 2024-07-12T01:46:58Z │
│ 6 │ v1 │ Pod │ grafana-alloy-97c8n │ monitoring │ 2024-07-12T01:49:46Z │
╰───┴────────────┴──────┴────────────────────────────────────┴────────────┴──────────────────────╯
One challenge is that when you kubectl returns json, there is a lot of data. You can use the nushell columns command to understand all of the columns that are available.
kubectl get pods -o json | from json | get items | flatten | columns
╭────┬───────────────────────────────╮
│ 0 │ apiVersion │
│ 1 │ kind │
│ 2 │ annotations │
│ 3 │ creationTimestamp │
│ 4 │ generateName │
│ 5 │ labels │
│ 6 │ name │
│ 7 │ namespace │
│ 8 │ ownerReferences │
│ 9 │ resourceVersion │
│ 10 │ uid │
│ 11 │ affinity │
│ 12 │ containers │
│ 13 │ dnsPolicy │
│ 14 │ enableServiceLinks │
│ 15 │ nodeName │
│ 16 │ preemptionPolicy │
│ 17 │ priority │
│ 18 │ restartPolicy │
│ 19 │ schedulerName │
│ 20 │ securityContext │
│ 21 │ serviceAccount │
│ 22 │ serviceAccountName │
│ 23 │ terminationGracePeriodSeconds │
│ 24 │ tolerations │
│ 25 │ volumes │
│ 26 │ conditions │
│ 27 │ containerStatuses │
│ 28 │ hostIP │
│ 29 │ hostIPs │
│ 30 │ phase │
│ 31 │ podIP │
│ 32 │ podIPs │
│ 33 │ qosClass │
│ 34 │ startTime │
│ 35 │ automountServiceAccountToken │
│ 36 │ initContainers │
│ 37 │ initContainerStatuses │
╰────┴───────────────────────────────╯
Now that we have access to this metadata, we can do all sorts of interesting queries on our data.
Sorting
Sort by the created date.
# Get the oldest pods
kubectl get pods -Ao json | from json | get items | flatten | sort-by creationTimestamp | select kind name namespace creationTimestamp | first 5
╭───┬──────┬──────────────────────────────────────┬──────────────────────┬──────────────────────╮
│ # │ kind │ name │ namespace │ creationTimestamp │
├───┼──────┼──────────────────────────────────────┼──────────────────────┼──────────────────────┤
│ 0 │ Pod │ coredns-59b4f5bbd5-nswpf │ kube-system │ 2023-06-19T23:00:16Z │
│ 1 │ Pod │ debug-7b578644b5-mkv6d │ default │ 2023-06-22T21:53:34Z │
│ 2 │ Pod │ api-6bfbf64b59-gqf4w │ default │ 2024-01-19T02:54:50Z │
│ 3 │ Pod │ homer-d58596598-8jkfn │ default │ 2024-05-15T13:35:12Z │
│ 4 │ Pod │ kubernetes-dashboard-64d75468c-pzcsx │ kubernetes-dashboard │ 2024-05-15T13:35:12Z │
╰───┴──────┴──────────────────────────────────────┴──────────────────────┴──────────────────────╯
# Get the newest pods
kubectl get pods -Ao json | from json | get items | flatten | sort-by creationTimestamp --reverse | select kind name namespace creationTimestamp | first 5
╭───┬──────┬─────────────────────────────────────────────────────┬─────────────────┬──────────────────────╮
│ # │ kind │ name │ namespace │ creationTimestamp │
├───┼──────┼─────────────────────────────────────────────────────┼─────────────────┼──────────────────────┤
│ 0 │ Pod │ instance-manager-e-0ca1593f370359a01871d9fdfe0dae2f │ longhorn-system │ 2024-07-14T15:33:19Z │
│ 1 │ Pod │ instance-manager-r-0ca1593f370359a01871d9fdfe0dae2f │ longhorn-system │ 2024-07-14T15:33:19Z │
│ 2 │ Pod │ instance-manager-e-2624c5ccb0ea251f9017c48e42e2996b │ longhorn-system │ 2024-07-14T15:33:16Z │
│ 3 │ Pod │ instance-manager-r-2624c5ccb0ea251f9017c48e42e2996b │ longhorn-system │ 2024-07-14T15:33:16Z │
│ 4 │ Pod │ longhorn-driver-deployer-9d85f7675-q45zx │ longhorn-system │ 2024-07-14T06:29:08Z │
╰───┴──────┴─────────────────────────────────────────────────────┴─────────────────┴──────────────────────╯
Yes, it is true that you could do all of this with kubectl, but I can never remember the correct way to use jsonpath and/or jq. I find the nushell syntax a lot easier to work with.
Filtering
Get all of the pods created in June.
kubectl get pods -Ao json | from json | get items | flatten | select kind name namespace creationTimestamp | into datetime creationTimestamp | insert month { $in.creationTimestamp | date to-record | get month } | where month == 6 | first 5
╭───┬──────┬──────────────────────────────────┬─────────────────┬───────────────────┬───────╮
│ # │ kind │ name │ namespace │ creationTimestamp │ month │
├───┼──────┼──────────────────────────────────┼─────────────────┼───────────────────┼───────┤
│ 0 │ Pod │ longhorn-csi-plugin-jmtdf │ longhorn-system │ a month ago │ 6 │
│ 1 │ Pod │ longhorn-csi-plugin-nl8ls │ longhorn-system │ a month ago │ 6 │
│ 2 │ Pod │ csi-resizer-6ddc566bd6-lvzjk │ longhorn-system │ a month ago │ 6 │
│ 3 │ Pod │ csi-attacher-6fd696d46d-88qc5 │ longhorn-system │ a month ago │ 6 │
│ 4 │ Pod │ csi-provisioner-7797d44fd9-5hwft │ longhorn-system │ a month ago │ 6 │
╰───┴──────┴──────────────────────────────────┴─────────────────┴───────────────────┴───────╯
This is pretty verbose. But, I like that I can read the command and pretty easily parse out what is happening. I am also very new to nushell, so there is probably a more efficient way to do this.
Wrap up
Hopefully this post gives you an idea of how nushell can help you interact with your Kubernetes cluster. As I come across more handy snippets I will update this blog post with them.