So, like others have pointed out, Kubernetes doesn&#39;t support stop/pause of current state of pod and resume when needed. However, you can still achieve it by having no working deployments which is setting number of replicas to 0.

```
kubectl scale --replicas=0 deployment/&lt;your-deployment&gt;
```


see the help

```
# Set a new size for a Deployment, ReplicaSet, Replication Controller, or StatefulSet.
kubectl scale --help
                                  
```

Scale also allows users to specify one or more preconditions for the scale action.

If `--current-replicas` or `--resource-version` is specified, it is validated before the scale is attempted, and it is
guaranteed that the precondition holds true when the scale is sent to the server.

**Examples:**
```
  # Scale a replicaset named &#39;foo&#39; to 3.
  kubectl scale --replicas=3 rs/foo

  # Scale a resource identified by type and name specified in &quot;foo.yaml&quot; to 3.
  kubectl scale --replicas=3 -f foo.yaml

  # If the deployment named mysql&#39;s current size is 2, scale mysql to 3.
  kubectl scale --current-replicas=2 --replicas=3 deployment/mysql

  # Scale multiple replication controllers.
  kubectl scale --replicas=5 rc/foo rc/bar rc/baz

  # Scale statefulset named &#39;web&#39; to 3.
  kubectl scale --replicas=3 statefulset/web
```

No. It is not possible to stop a pod and resume later when required. However, You can consider the below approach.

In k8s, pods are abstracted using a service. One way I can think of isolating the pod(s) is by updating the pod selector in the service definition. 
That way you can control the traffic to pod(s) using service definition. Whenever you want to restore the traffic update the pod selector value back to what it was in the service definition.

With Kubernets, it&#39;s not possible to stop/pause a Pod. However, you can delete a Pod, given the fact you have the manifest to bring that back again.

If you want to delete a Pod, you can run the following `kubectl` command:

    kubectl delete -n default pod &lt;your-pod-name&gt;

I found that there are several ways to handle user&#39;s text input with hooks. What is more preferable or proper way to handle an input with hooks? Which would you use?

1) The simplest hook to handle input, but more fields you have, more repetitive code you have to write.

    const [username, setUsername] = useState(&#39;&#39;);
    const [password, setPassword] = useState(&#39;&#39;);

events:

    onChange={event =&gt; setPassword(event.target.value)}
    onChange={event =&gt; setUsername(event.target.value)}

2) Similar to above example, but with dynamic key name

    const [inputValues, setInputValues] = useState({
      username: &#39;&#39;, password: &#39;&#39;
    });
    
    const handleOnChange = event =&gt; {
      const { name, value } = event.target;
      setInputValues({ ...inputValues, [name]: value });
    };

event:

    onChange={handleOnChange}

3) An alternative to `useState`, and as said on ReactJS docs, `useReducer` is usually preferable to `useState`.

    const [inputValues, setInputValues] = useReducer(
      (state, newState) =&gt; ({ ...state, ...newState }),
      {username: &#39;&#39;, password: &#39;&#39;}
    );
    
    const handleOnChange = event =&gt; {
      const { name, value } = event.target;
      setInputValues({ [name]: value });
    };

event:

    onChange={handleOnChange}

4) `useCallback` will return a memoized version of the callback that only changes if one of the dependencies has changed.

    const [inputValues, setInputValues] = useState({ 
      username: &#39;&#39;, password: &#39;&#39; 
    });
    
    const handleOnChange = useCallback(event =&gt; {
      const { name, value } = event.target;
      setInputValues({ ...inputValues, [name]: value });
    });

event:

    onChange={handleOnChange}

Handle an input with React hooks

I&#39;ve recently seen the following code:

    public class Person
    {
        //line 1
    	public string FirstName { get; }

        //line 2
    	public string LastName { get; } = null!;

        //assign null is possible
    	public string? MiddleName { get; } = null;
    
    	public Person(string firstName, string lastName, string middleName)
    	{
    		FirstName = firstName;
    		LastName = lastName;
    		MiddleName = middleName;
    	}
    
    	public Person(string firstName, string lastName)
    	{
    		FirstName = firstName;
    		LastName = lastName;
    		MiddleName = null;
    	}
    }

Basically, I try to dig into new c# 8 features. One of them is `NullableReferenceTypes`. &lt;br /&gt;
Actually, there&#39;re a lot of articles and information about it already. E.g. [this article][1] is quite good. &lt;br/&gt;
But I didn&#39;t find any information about this new statement `null!` &lt;br/&gt;
Can someone provide me an explanation for it? &lt;br/&gt;
Why do I need to use this? &lt;br/&gt;
And what is the difference between `line1` and `line2`?


  [1]: https://praeclarum.org/2018/12/17/nullable-reference-types.html

What does null! statement mean?

I have a MySQL pod running in my cluster.&lt;br&gt; I need to temporarily pause the pod from working without deleting it, something similar to docker where the `docker stop container-id` cmd will stop the container not delete the container.&lt;br&gt; Are there any commands available in kubernetes to pause/stop a pod?

how to stop/pause a pod in kubernetes

<p>I have a MySQL pod running in my cluster.<br> I need to temporarily pause the pod from working without deleting it, something similar to docker where the <code>docker stop container-id</code> cmd will stop the container not delete the container.<br> Are there any commands available in kubernetes to pause/stop a pod?</p>


I want my [tests folder separate][1] to my application code. My project structure is like so

    myproject/
      myproject/
        myproject.py
        moduleone.py
      tests/
        myproject_test.py

myproject.py

    from moduleone import ModuleOne
    
    class MyProject(object)
    ....

myproject_test.py

    from myproject.myproject import MyProject
    import pytest

    ...

I use `myproject.myproject` since I use the command
 
    python -m pytest

from the project root directory `./myproject/`

However, then the imports within those modules fail with


 &gt; E   ModuleNotFoundError: No module named &#39;moduleone&#39;


I am running Python 3.7 and have read that since 3.3, empty `__init__` files are no longer needed which means my project becomes an [implicit namespace package][2]

However, I have tried adding an `__init__.py` file in `myproject/myproject/` and also tried adding a `conftest.py` file in `myproject/` but  neither works


I have [read answers][3] that say to [mess with the paths][4] and then upvoted comments in other questions saying [not to][5].

What is the correct way and what am I missing?

**EDIT;**

Possibly related, I used a `requirements.txt` to install pytest using pip. Could this be related? And if so, what is the correct way to install pytest in this case?

**EDIT 2:**

One of the paths in `sys.path` is `/usr/src/app/` which is a docker volume lined to `/my/local/path/myproject/`.

Should the volume be `/my/local/path/myproject/myproject/` instead?


  [1]: https://docs.pytest.org/en/latest/goodpractices.html#tests-outside-application-code
  [2]: https://stackoverflow.com/a/52812525/817379
  [3]: https://stackoverflow.com/a/48694855/817379
  [4]: https://stackoverflow.com/a/49605901/817379
  [5]: https://stackoverflow.com/q/49723266/817379

ModuleNotFoundError with pytest

I am looking to pick up a docker image to build a java app and looking at the variants of the OpenJDK images available.
I am looking here https://github.com/docker-library/openjdk/tree/master/8/jdk and see alpine, slim and windows.
What are the differences between these and what does each variant give?

Docker images - types. Slim vs slim-stretch vs stretch vs alpine

There is a previous question (https://stackoverflow.com/questions/48167955/docker-unknown-flag-mount) facing the same error that was due to having an out-of-date version of Docker running. I have an up-to-date version of Docker running.

I have the following `Dockerfile`:

    FROM continuumio/miniconda3
    
    RUN --mount=type=ssh pip install git+ssh://git@github.com/myrepo/myproject.git@develop
    RUN conda install numpy
    ...

According to the [documentation][1], I should be able to simply run `docker build --ssh default .`. However, I receive the following error:

    Sending build context to Docker daemon  2.048kB
    Error response from daemon: Dockerfile parse error line 3: Unknown flag: mount

Output of `docker version`:

    Client: Docker Engine - Community
     Version:           18.09.2
     API version:       1.39
     Go version:        go1.10.8
     Git commit:        6247962
     Built:             Sun Feb 10 04:12:39 2019
     OS/Arch:           darwin/amd64
     Experimental:      false
    
    Server: Docker Engine - Community
     Engine:
      Version:          18.09.2
      API version:      1.39 (minimum version 1.12)
      Go version:       go1.10.6
      Git commit:       6247962
      Built:            Sun Feb 10 04:13:06 2019
      OS/Arch:          linux/amd64
      Experimental:     true

I would like to build a Docker image without exposing my private SSH credentials, and this seemed to be the supported method. Anyone have thoughts on what&#39;s causing the issue?

  [1]: https://docs.docker.com/develop/develop-images/build_enhancements/#using-ssh-to-access-private-data-in-builds

Error response from daemon: Dockerfile parse error Unknown flag: mount

I have a problem with my MySQL error log which currently mostly consists of &quot;mbind: Operation not permitted&quot; lines (see below). Why does it happen and how do I fix it?

It&#39;s the &quot;mostly&quot; part that bothers me. As you can see below, not all lines are &quot;mbind: Operation not permitted&quot;. I suspect that MySQL query errors should be instead of that line, but for some reason they can&#39;t be written into the file.

MySQL itself is a Docker container where log files are volumed via:

    volumes:
    - ./mysql/log:/var/log/mysql

What&#39;s interesting is that:

- &quot;docker logs mysql_container&quot; shows nothing...
- slow.log, which resides in the same volume folder, is completely OK and has real slow log lines in it, no &quot;mbind: Operation not permitted&quot; whatsoever!
- same as slow.log goes to general.log — no problem here, either

Any ideas? Thank you in advance.

```
2019-04-07T12:56:22.478504Z 0 [Warning] [MY-011070] [Server] &#39;Disabling symbolic links using --skip-symbolic-links (or equivalent) is the default. Consider not using this option as it&#39; is deprecated and will be removed in a future release.
2019-04-07T12:56:22.478533Z 0 [Warning] [MY-011068] [Server] The syntax &#39;expire-logs-days&#39; is deprecated and will be removed in a future release. Please use binlog_expire_logs_seconds instead.
2019-04-07T12:56:22.478605Z 0 [System] [MY-010116] [Server] /usr/sbin/mysqld (mysqld 8.0.15) starting as process 1
2019-04-07T12:56:22.480115Z 0 [Warning] [MY-013242] [Server] --character-set-server: &#39;utf8&#39; is currently an alias for the character set UTF8MB3, but will be an alias for UTF8MB4 in a future release. Please consider using UTF8MB4 in order to be unambiguous.
2019-04-07T12:56:22.480122Z 0 [Warning] [MY-013244] [Server] --collation-server: &#39;utf8_general_ci&#39; is a collation of the deprecated character set UTF8MB3. Please consider using UTF8MB4 with an appropriate collation instead.
mbind: Operation not permitted
mbind: Operation not permitted
mbind: Operation not permitted
mbind: Operation not permitted
mbind: Operation not permitted
mbind: Operation not permitted
mbind: Operation not permitted
mbind: Operation not permitted
mbind: Operation not permitted
mbind: Operation not permitted
mbind: Operation not permitted
mbind: Operation not permitted
mbind: Operation not permitted
mbind: Operation not permitted
mbind: Operation not permitted
mbind: Operation not permitted
mbind: Operation not permitted
mbind: Operation not permitted
[same line goes forever]
```

P.S. MySQL starts and runs well, no problem with that. It&#39;s just this error.log that keeps bothering me and prevents me from seeing actual errors.

How to fix &quot;mbind: Operation not permitted&quot; in mysql error log

When building Docker images with `DOCKER_BUILDKIT=1`, there is a very cool progress indicator but no command output. How do I see the command output to debug my build?

When using BuildKit with Docker, how do I see the output of RUN commands?

When deploying a service via a Helm Chart, the installation failed because the `tiller` serviceaccount was not allowed to create a `ServiceMonitor` resource.

Note:

 - `ServiceMonitor` is a CRD defined by the Prometheus Operator to automagically get metrics of running containers in Pods.
 - Helm Tiller is installed in a single namespace and the RBAC has been setup using Role and RoleBinding.

I wanted to verify the permissions of the `tiller` serviceaccount.  
`kubectl` has the `auth can-i` command, queries like these (see below) always return `no`.

 - `kubectl auth can-i list deployment --as=tiller`
 - `kubectl auth can-i list deployment --as=staging:tiller`

What is the proper way to check permissions for a serviceaccount?  
How to enable the `tiller` account to create a ServiceMonitor resource?

Kubernetes check serviceaccount permissions

Say, I have two namespaces k8s-app1 and k8s-app2

I can list all pods from specific namespace using the below command
````
kubectl get pods -n &lt;namespace&gt;
````

We need to append namespace to all commands to list objects from the respective namespaces. Is there a way to set specific namespace and list objects without including the namespace explicitly?

How to switch namespace in kubernetes

I&#39;m following that tutorial (https://www.baeldung.com/spring-boot-minikube)
I want to create Kubernetes deployment in yaml file (simple-crud-dpl.yaml):

```
apiVersion: apps/v1
kind: Deployment
metadata:
  name: simple-crud
spec:
  selector:
      matchLabels:
        app: simple-crud
  replicas: 3
  template:
    metadata:
      labels:
        app: simple-crud
    spec:
      containers:
        - name: simple-crud
          image: simple-crud:latest
          imagePullPolicy: Never
          ports:
            - containerPort: 8080
```

but when I run ```kubectl create -f simple-crud-dpl.yaml``` i got:
```error: SchemaError(io.k8s.api.autoscaling.v2beta2.MetricTarget): invalid object doesn&#39;t have additional properties```

I&#39;m using the newest version of kubectl: 
```
kubectl version
Client Version: version.Info{Major:&quot;1&quot;, Minor:&quot;10&quot;, GitVersion:&quot;v1.10.11&quot;, GitCommit:&quot;637c7e288581ee40ab4ca210618a89a555b6e7e9&quot;, GitTreeState:&quot;clean&quot;, BuildDate:&quot;2018-11-26T14:38:32Z&quot;, GoVersion:&quot;go1.9.3&quot;, Compiler:&quot;gc&quot;, Platform:&quot;darwin/amd64&quot;}
Server Version: version.Info{Major:&quot;1&quot;, Minor:&quot;14&quot;, GitVersion:&quot;v1.14.0&quot;, GitCommit:&quot;641856db18352033a0d96dbc99153fa3b27298e5&quot;, GitTreeState:&quot;clean&quot;, BuildDate:&quot;2019-03-25T15:45:25Z&quot;, GoVersion:&quot;go1.12.1&quot;, Compiler:&quot;gc&quot;, Platform:&quot;linux/amd64&quot;}
```

I&#39;m also using minikube locally as it&#39;s described in tutorial. Everything is working till deployment and service. I&#39;m not able to do it.

Kubernetes create deployment unexpected SchemaError

I am trying to get the namespace of the currently used Kubernetes context using `kubectl`.

I know there is a command `kubectl config get-contexts` but I see that it cannot output in json/yaml. The only script I&#39;ve come with is this:

```bash
kubectl config get-contexts --no-headers | grep &#39;*&#39; | grep -Eo &#39;\S+$&#39;
```

How to get the current namespace of current context using kubectl

I inherited a Kubernetes/Docker setup, and I accidentally crashed the pod by changing something relating to the DB password.

I am trying to troubleshoot this.

I don&#39;t have much Kubernetes or Docker experience, so I&#39;m still learning how to do things.

The value is contained inside the db-user-pass credential I believe, which is an Opaque type secret.

I&#39;m describing it:

    kubectl describe secrets/db-user-pass
    Name:         db-user-pass
    Namespace:    default
    Labels:       &lt;none&gt;
    Annotations:  &lt;none&gt;
    
    Type:  Opaque
    
    Data
    ====
    password:  16 bytes
    username:  13 bytes

but I have no clue how to get any data from this secret. The example on the Kubernetes site seems to assume I&#39;ll have a base64 encoded string, but I can&#39;t even seem to get that. How do I get the value for this?

Content Type	Original Author	Original Content on Stackoverflow
Question	AATHITH RAJENDRAN	View Question on Stackoverflow
Solution 1 - Docker	sulabh chaturvedi	View Answer on Stackoverflow
Solution 2 - Docker	P Ekambaram	View Answer on Stackoverflow
Solution 3 - Docker	Anjana Silva	View Answer on Stackoverflow

how to stop/pause a pod in kubernetes

Docker Problem Overview

Docker Solutions

Solution 1 - Docker

Solution 2 - Docker

Solution 3 - Docker

What does null! statement mean?

Handle an input with React hooks

Attributions