What is HostProcess containers in AKS?.
Tags: azure, kubernetes, containers, aks
Published: 2022-05-27 01:44:48

HostProcess / Privileged containers lengthen the Windows container model to allow a wider vary of Kubernetes cluster administration scenarios. HostProcess containers run at once on the host and preserve behavior and access similar to that of a ordinary process. 

HostProcess containers allow users to package and distribute management operations and functionalities that require host access whilst protecting versioning and deployment strategies provided by means of containers.

A privileged DaemonSet can elevate out adjustments or reveal a Linux host on Kubernetes however not Windows hosts. HostProcess containers are the Windows equal of host elevation.

## Limitations


- HostProcess containers require Kubernetes 1.23 or greater.
- HostProcess containers require containerd 1.6 or higher container runtime.
- HostProcess pods can only include HostProcess containers. This is a current predicament of the Windows operating system. Non-privileged Windows containers cannot share a vNIC with the host IP namespace.
- HostProcess containers run as a system on the host. The solely isolation these containers have from the host is the resource constraints imposed on the HostProcess person account.
- Filesystem isolation and Hyper-V isolation are not supported for HostProcess containers.
- Volume mounts are supported and are set up under the container volume. See Volume Mounts.
- A confined set of host consumer accounts are accessible for Host Process containers through default. See Choosing a User Account.
- Resource limits such as disk, memory, and cpu count, work the same way as trend as processes on the host.
- Named pipe mounts and Unix domain sockets are now not without delay supported, but can be accessed on their host path, for instance \\.\pipe\*.


## Run a HostProcess workload

To use HostProcess features with your deployment, set privileged: true, hostProcess: true, and hostNetwork: true:

```
spec:
      ...
      containers:
          ...
          securityContext:
            privileged: true
            windowsOptions:
              hostProcess: true
              ...
      hostNetwork: true
      ...

```

To run an example workload that uses HostProcess features on an existing AKS cluster, create [kcdhostprocess.yaml](https://github.com/MakendranG/AKS_HostProcess-Containers/blob/main/kcdhostprocess.yaml).

The example workload can be run using kubectl.

```
kubectl apply -f kcdhostprocess.yaml
```

You should see the following output:


```
$ kubectl apply -f kcdhostprocess.yaml
daemonset.apps/privileged-daemonset created
```


The features of HostProcess can be verified by viewing the logs.

The name of the Pod can be found in the kube-systemnamespace.

```
$ kubectl get pods --namespace kube-system

NAME                                  READY   STATUS    RESTARTS   AGE
...
privileged-daemonset-12345            1/1     Running   0          2m13s
```

You can use the log to view the logs and verify the administrator rights.

```
$ kubectl logs privileged-daemonset-12345 --namespace kube-system
InvalidOperation: Unable to find type [Security.Principal.WindowsPrincipal].
Process has admin rights:
```


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