kubectl YML : what type of file is this and how to run it

Question

I can see a way to create kubectl command like this where I can pass some parameterize values ad well.

My question is, with what type of file we will save this, Is this a bash script? and how to run and supply the parameter?

export SECRET_NAME="my-app.secret"

cat <<EOF | kubectl apply -f -
 apiVersion: v1
 kind: Secret
 metadata:
 name: $SECRET_NAME
 type: Opaque
 data:
 password: $(echo -n "s33msi4" | base64 -w0)
 username: $(echo -n "jane" | base64 -w0)
EOF

Answer 1

Yes, it can be treated as a bash script. As Jetchisel already mentioned in his comment, it contains a structure called Here Document used with cat command but it also contains export command which sets and exports a variable. So as a whole it can be treated as a simple bash script with 2 instructions.

In order to run it and create a new Secret object (which is your ultimate goal), follow these steps:

1. Fix the indentation which is crucial in yaml files:

export SECRET_NAME="my-app.secret"

cat <<EOF | kubectl apply -f -
 apiVersion: v1
 kind: Secret
 metadata:
   name: $SECRET_NAME
 type: Opaque
 data:
   password: $(echo -n "s33msi4" | base64 -w0)
   username: $(echo -n "jane" | base64 -w0)
EOF

2. Save the above content as a file. You can call it secret.sh.
3. Source it (source and . are the same command):

. secret.sh

4. You should see the following message:

secret/my-app.secret created

Alternatvely you can paste it directly into the console. As you can see, it also works:

### don't copy it, this is the example console output 
### you will see once you paste the above script in your bash shell

$ export SECRET_NAME="my-app.secret"
$
$ cat <<EOF | kubectl apply -f -
>  apiVersion: v1
>  kind: Secret
>  metadata:
>    name: $SECRET_NAME
>  type: Opaque
>  data:
>    password: $(echo -n "s33msi4" | base64 -w0)
>    username: $(echo -n "jane" | base64 -w0)
> EOF
secret/my-app.secret created