agnhost

README

Agnhost

Overview

There are significant differences between Linux and Windows, especially in the way something can be obtained or tested. For example, the DNS suffix list can be found in /etc/resolv.conf on Linux, but on Windows, such file does not exist, the same information could retrieved through other means. To combat those differences, agnhost was created.

agnhost is an extendable CLI that behaves and outputs the same expected content, no matter the underlying OS. The name itself reflects this idea, being a portmanteau word of the words agnost and host.

The image was created for testing purposes, reducing the need for having different test cases for the same tested behaviour.

Usage

The agnhost binary is a CLI with the following subcommands:

• dns-suffix: It will output the host's configured DNS suffix list, separated by commas.
• dns-server-list: It will output the host's configured DNS servers, separated by commas.
• etc-hosts: It will output the contents of host's hosts file. This file's location is /etc/hosts on Linux, while on Windows it is C:/Windows/System32/drivers/etc/hosts.
• pause: It will pause the execution of the binary. This can be used for containers which have to be kept in a Running state for various purposes, including executing other agnhost commands.
• help: Prints the binary's help menu. Additionally, it can be followed by another subcommand in order to get more information about that subcommand, including its possible arguments.

For example, let's consider the following pod.yaml file:

    apiVersion: v1
    kind: Pod
    metadata:
      name: test-agnhost
    spec:
      containers:
      - args:
        - dns-suffix
        image: gcr.io/kubernetes-e2e-test-images/agnhost:1.0
        name: agnhost
      dnsConfig:
        nameservers:
        - 1.1.1.1
        searches:
        - resolv.conf.local
      dnsPolicy: None

After we've used it to create a pod:

    kubectl create -f pod.yaml

We can then check the container's output to see what is DNS suffix list the Pod was configured with:

    kubectl logs pod/test-agnhost

The output will be resolv.conf.local, as expected. Alternatively, the Pod could be created with the pause argument instead, allowing us execute multiple commands:

    kubectl exec test-agnhost -- /agnhost dns-suffix
    kubectl exec test-agnhost -- /agnhost dns-server-list

Image

The image can be found at gcr.io/kubernetes-e2e-test-images/agnhost:1.0 for Linux containers, and e2eteam/agnhost:1.0 for Windows containers. In the future, the same repository can be used for both OSes.