Previous: kubectl for CKAD - exercise 9 - expose a pod with NodePort service, delete lines in Vim

First things first

Put your mouse away, forget you have a touchpad and keep your hands on the keyboard.

For resources that cannot be created with kubectl, we need to copy YAML definitions from kubernetes.io. Sometimes we need to copy some lines into a deployment yaml, but there is only a pod yaml having the lines we need. When we paste the lines from a pod yaml into the deployment yaml, the indentation is incorrect. In this exercise, we will see how to fix the indentation.

Scenario

Create a deployment which uses an emptyDir: {} volume named redis-storage and mounts it to the mount path /data/redis

Open a new deployment yaml manifest directly in Vim

kubectl create deploy testdep --image nginx:alpine --dry-run=client -o yaml | vim -

Use the alias k and the bash variable $dry if you have already created them in your .bashrc file. (kubectl for CKAD - exercise 8 - use bash exported variables in Vim 2)

Output in Vim:

apiVersion: apps/v1
kind: Deployment
metadata:
  creationTimestamp: null
  labels:
    app: testdep
  name: testdep
spec:
  replicas: 1
  selector:
    matchLabels:
      app: testdep
  strategy: {}
  template:
    metadata:
      creationTimestamp: null
      labels:
        app: testdep
    spec:
      containers:
      - image: nginx:alpine
        name: nginx
        resources: {}
status: {}

To keep the pasted yaml lines properly formatted, we need to set Vim up:

:set paste

For proper yaml formatting, the indentation needs to be done with spaces. To see if yaml is not accidentally indented with tabs ( ^I ), make tabs visible :

:set list

Copy lines for volumes and volumeMounts from the pod yaml on kubernetes.io - paste it into a Vim document

Open the page https://kubernetes.io/docs/tasks/configure-pod-container/configure-volume-storage/#configure-a-volume-for-a-pod and have a look at the pods/storage/redis.yaml.

This is the part we want to copy and paste into our deployment yaml:

    volumeMounts:
    - name: redis-storage
      mountPath: /data/redis
  volumes:
  - name: redis-storage
    emptyDir: {}

Practice using the Firefox browser in Linux (i hope, you are using a linux machine all the time).

Select the yaml text with the mouse and copy it.

control c

Back in Vim, look up the container name (name: nginx), then jump right to it by searching in Vim starting at the bottom

G               # jump down to the last line
?ngi            # use ? to search upwards from the bottom to top. Be lazy, there is no need to write the whole word nginx
Enter
n               # 'n'ew search up - repeats the search upwards if needed

With the cursor positioned on the name: nginx, paste the copied yaml lines into the deployment yaml:

o                  # o opens a new line be`low` (as in `low`ercase `o`) the current line and switches to INSERT mode, allowing us to paste
shift control v

If we keep the indentation from the pod yaml definition, the deployment will not work.

 ...   
    spec:
      containers:
      - image: nginx:alpine
        name: nginx
    volumeMounts:
    - name: redis-storage
      mountPath: /data/redis
  volumes:
  - name: redis-storage
    emptyDir: {}
        resources: {}
status: {}

To correct the indentation, we will nudge the copied lines to the right, so that it looks like this:

...
    spec:
      containers:
      - image: nginx:alpine
        name: nginx
        volumeMounts:
        - name: redis-storage
          mountPath: /data/redis
      volumes:
      - name: redis-storage
        emptyDir: {}
        resources: {}
status: {}

!!! Now reset the paste mode back to nopaste, otherwise the tab expansion (nudging) will not work. We need Vim to expand tabs into two spaces when we press Tab, instead of inserting the ^Icharacter.

ESC                  # 'ESC'ape from INSERT mode to NORMAL modes
:set nopaste

Search upwards for the first line to be nudged

?vol                 # use ? to search upwards from the bottom to top. Be lazy, there is no need to write the whole word volumeMounts
Enter
n                    # new search up - repeat the search upwards until the cursor lands the first line of the copied block

Set Vim up for correct indentation

:set expandtab       # :set et    works as well
:set tabstop=2       # :set ts=2
:set shiftwidth=2    # :set sw=2

With the cursor now positioned on the first line to be nudged, the question is, how many lines do we need to nudge?

Set Vim up to show line numbers and relative line numbers

:set nu           # show 'nu'mbers
:set rnu          # show 'r'elative 'nu'mbers

Or do it in one line

:set nu rnu

For correct yaml formatting, indentation needs to be done with spaces only. Anytime there are some ^I characters visible, something has gone wrong.

If not done already - to check if we are not indenting the lines with tabs, make the tabs visible.

:set list

Ignore the $ character, :set list shows us also the end of the line.

Notice, that the relative numbering starts below the current line, so we need to add 1 to the number of lines to nudge (5 + 1).

  4     spec:$
  3       containers:$
  2       - image: nginx:alpine$
  1         name: nginx$
23      volumeMounts:$
  1     - name: redis-storage$
  2       mountPath: /data/redis$
  3   volumes:$
  4   - name: redis-storage$
  5     emptyDir: {}$
  6         resources: {}$
  7 status: {}$

Indent 6 lines

6>>              # nudge 6 lines to the right
.                # dot repeats it once more for all 6 lines

--- if you need to go back, use undo ---
u

write (save) the document

ESC                    # 'ESC'ape from INSERT mode 
:w testdep.yaml        # 'w'rite (save) the document

Remember, we don’t leave Vim for this:

If you have already set up the bash variable / shortcut ka in the previous exercises use it like this directly from inside Vim

:!$ka -f %             # Run `kubectl apply` directly from inside Vim

otherwise, run kubectl apply

:!kubectl apply -f %   # % references the current file name

If everything is fine with the yaml definition, testdep.yaml gets applied, deployment is created

kubectl get deploy -o wide             # view the deployment, -o wide is optional, it shows more info about resources

Scenario continued

If there is an error and the deployment has not been created, read the error, then simply press Enter go back to Vim, edit the yaml file and correct the error.

write (save) the document

ESC                    # 'ESC'ape from INSERT mode 
:w testdep.yaml        # 'w'rite (save) the document

Repeat running kubectl apply directly from Vim re-using the previous command

:up arrow              # repeat to find the command you used to apply the yaml
Enter

If the error is fixed in the yaml file, testdep.yaml gets applied, deployment is created

k get deploy -o wide             # view the deployment, -o wide is optional, it shows more info about resources

Congratulations!

Practice these steps to make editing documents in Vim second nature, copying yaml text from a browser, pasting it into Vim documents and correcting the indentation.

Next: kubectl for CKAD - exercise 11 - search and replace in Vim