How to pass "--command" to "kubectl run" that also uses "--overrides"

Question

I noticed a strange behavior while experimenting with kubectl run :

• When the command to be executed is passed as option flag --command -- /bin/sh -c "ls -lah" > OK

  kubectl run nodejs --image=node:lts-alpine \
    --restart=Never --quiet -i --rm \
    --command -- /bin/sh -c "ls -lah"
  

• When command to be executed is passed in --overrides with "command": [ "ls", "-lah" ] > OK

  kubectl run nodejs --image=node:lts-alpine \
    --restart=Never \
    --overrides='
    {
      "kind": "Pod",
      "apiVersion": "v1",
      "metadata": {
        "name": "nodejs"
      },
      "spec": {
        "volumes": [
          {
            "name": "host-volume",
            "hostPath": {
              "path": "/home/dferlay/Sources/df-sdc/web/themes/custom/"
            }
          }
        ],
        "containers": [
          {
            "name": "nodejs",
            "image": "busybox",
            "command": [
              "ls",
              "-lah"
            ],
            "workingDir": "/app",
            "volumeMounts": [
              {
                "name": "host-volume",
                "mountPath": "/app"
              }
            ],
            "terminationMessagePolicy": "FallbackToLogsOnError",
            "imagePullPolicy": "IfNotPresent"
          }
        ],
        "restartPolicy": "Never",
        "securityContext": {
          "runAsUser": 1000,
          "runAsGroup": 1000
        }
      }
    }
    ' \
    --quiet -i --rm
  

• When the command to be executed is passed as option flag --command -- /bin/sh -c "ls -lah" and --overrides is used for something else (volume for instance) > KO

  kubectl run nodejs --image=node:lts-alpine --restart=Never \
    --overrides='
    {
      "kind": "Pod",
      "apiVersion": "v1",
      "metadata": {
        "name": "nodejs"
      },
      "spec": {
        "volumes": [
          {
            "name": "host-volume",
            "hostPath": {
              "path": "/home/dferlay/Sources/df-sdc/web/themes/custom/"
            }
          }
        ],
        "containers": [
          {
            "name": "nodejs",
            "image": "busybox",
            "workingDir": "/app",
            "volumeMounts": [
              {
                "name": "host-volume",
                "mountPath": "/app"
              }
            ],
            "terminationMessagePolicy": "FallbackToLogsOnError",
            "imagePullPolicy": "IfNotPresent"
          }
        ],
        "restartPolicy": "Never",
        "securityContext": {
          "runAsUser": 1000,
          "runAsGroup": 1000
        }
      }
    }
    ' \
    --quiet -i --rm --command -- /bin/sh -c "ls -lah"
  

So it looks like using --overrides prevents --command to be used.

However, I precisely need to use --command to bypass the array format expected by --overrides (ie. "command": [ "ls", "-lah" ]) because in my use case the command is a placeholder and cannot be known in advance.

• How can I do that ? Is there something I'm missing ?

FYI: kubectl version=v1.23.1+k3s2

Answer 1

You can bypass the array format by using the args field:

"command": [
 "sh",
 "-c"
],
"args": [ "pwd && id && node YOUR_COMMAND" ]