Proper way to directly pass yaml content to kubectl patch? - yaml

Question

Example of functional kubectl patch command:
# kubectl patch storageclass local-path \
-p '{"metadata": {"annotations": {"storageclass.kubernetes.io/is-default-class": "false"}}}'
In certain cases the patched key/values are too numerous, so is recommended to use a file instead:
# kubectl patch storageclass local-path --patch-file=file.yaml
I would like to use an alternative of this format, which returns an error:
cat << 'EOF' | kubectl patch storageclass local-path --patch-file -
metadata:
annotations:
storageclass.kubernetes.io/is-default-class: false
EOF
error: unable to read patch file: open -: no such file or directory
My goal is to use a dynamic way of pushing the patch data, without creating a file. What would be the correct format? Thank you.
Update: Based on provided documentation, I tried this format:
cat << 'EOF' | kubectl patch storageclass local-path --type=merge -p -
{
"metadata": {
"annotations": {
"storageclass.kubernetes.io/is-default-class": "false"
}
}
}
EOF
Error from server (BadRequest): json: cannot unmarshal array into Go value of type map[string]interface {}
Or:
kubectl patch storageclass local-path --type=merge -p << 'EOF'
{
"metadata": {
"annotations": {
"storageclass.kubernetes.io/is-default-class": "false"
}
}
}
EOF
error: flag needs an argument: 'p' in -p
What would be the correct format? I'm trying to avoid a very long line and keep a nice readable format.

Answer 1

If you look at the documentation of kubectl patch help that it is not a supported feature to pass the patch as you are trying to do because you either need to pass the patch as a json or from the file contains that contians the data.
You can pass something like this, but still you need to clean up the file you created here (auto.yaml).
$ cat <<EOF | echo "metadata:
> labels:
> app: testapp "> auto.yaml | kubectl patch pod pod-name --patch-file=auto.yaml
> EOF
For more information about EOF refer to the Here Document section in this document
For Updated question:
You are actually missing the ' quotation before starting the json and don't give - after -p. Give a try like this, this is working in our environment
$ cat <<EOF | kubectl patch deployments nginx --type=merge --patch '{
> "metadata":
> {
> "labels":
> {
> "check": "good"
> }
> }
> }'
> EOF