![what is kubernetes manifest what is kubernetes manifest](https://stackjourney.com/wp-content/uploads/2021/07/K8s-Horizontal-Pod-Autoscaler-HPA-Manifest-File-Explained.jpg)
"Overlaying" describes the process where separate files are layered over (or "stacked on top of") each other to create altered versions.
#What is kubernetes manifest how to
"Declarative" refers to the standard way to describe resources in Kubernetes: declaring what you want a resource to be and how to look and behave, in contrast to "imperative," which defines the process to create it. It's an Apache 2.0-licensed tool that generates custom versions of manifests by "overlaying" declarative specifications on top of existing ones. These are the basic tenets of Kustomize's approach. And you would keep the differences between versions small and simple.
![what is kubernetes manifest what is kubernetes manifest](https://cdn.thenewstack.io/media/2020/08/a14ea587-kube-01.png)
Ideally, you would be able to keep using your existing files in their original forms and produce variations without making permanent changes or copies that can easily diverge from the original and each other. At the extreme, this may make the files unusable and unreadable unless you use Helm to render them with the data values into a form that people (and Kubernetes) can understand and use. At some level, this can turn the templates into sort of "programmed YAML" files. Functions and pipes that join functions can also be added. In fact, the problem can be compounded when using templates due to copies having more placeholders and separate data values stored elsewhere. The templates are also still susceptible to the issues that copies of the files have. And, as templates, the original files are no longer easily parsable by anyone who looks at them.
![what is kubernetes manifest what is kubernetes manifest](https://miro.medium.com/max/5504/1*FWHZ6tqgLFJDqgEf8n9n0w.png)
They are no longer usable on their own they require an application or process like Helm to find or derive and fill in the values. Removing values and using placeholders fundamentally changes and adds complexity to the manifests, which are now templates. This is the approach the well-known tool Helm takes. eBook: A guide to Kubernetes for SREs and sysadmins.eBook: Running Kubernetes on your Raspberry Pi homelab.How to explain Kubernetes in plain terms.An introduction to enterprise Kubernetes.The resulting templates with the values filled in are rendered as valid manifests for Kubernetes. Values are usually supplied at deployment time, with placeholders replaced by values passed in from a command line or read in from a data file. That is, to make the manifests into generic "templates" by replacing static, hardcoded values with placeholders that can be filled in with any value. The parameterization approachĪnother approach is to create parameterized templates from the files. This, in turn, can dramatically affect usability and maintainability. People might miss important or significant updates to the original manifests, and they might end up using confusing variations of similar files.Īnd over time, the situation can worsen, and a significant amount of time can be spent just trying to keep things up to date. If copies of the copies are made, you can end up with something that diverges significantly from the original and even lose track of what was in the original. The problem becomes even worse if other people make their own copies and change them to suit their particular use case. Someone or something will have to monitor the original, figure out the differences, and merge them into the copy.
#What is kubernetes manifest update
Suppose you want to change a manifest to add a new resource or update a value in a manifest copy. This process works for the immediate use case, but things can quickly get out of sync or become unwieldy to manage. You make a copy, modify it in whatever way is appropriate, and save it with a different name or location. Typical approaches for reusing manifestsĪpproaches for reusing manifests have typically been rather brute force. What happens if someone else needs to work with your manifest but needs a slightly (or significantly) different version? Or what happens if someone wants to leverage your manifests for different stages or environments? You need to handle reuse and updates for the different use cases without losing track of your original version. Once those are created, you're done with managing your manifests, right? Well, it depends. These declarative YAML files for Kubernetes are usually known as "manifests." You might also have to set up secrets, ingresses, persistent volumes, and other supporting pieces. Even a simple microservice is likely to have a deployment.yaml, service.yaml, configmap.yaml, and other files. Working with Kubernetes requires defining and creating multiple "manifests" for the different types of objects in your application. Preparing to run a new (or convert an existing) application in Kubernetes takes work.