Kubernets plugins

Manage Kubernetes Plugins with Krew

There have been quite a few posts recently describing how to write custom plugins, now that the mechanism for creating and working with them has been made easier in upstream Kubernetes (as of v1.12). Here are the official plugin docs if you’re interested in learning more about how it all works.

One neat thing about the new plugin architecture is that they don’t need to be written in Go to be recognized by kubectl. There is a document in the Kubernetes repo that describes how to write your own custom plugin and even a helper library for making it easier to write plugins.

Instead of just writing another tutorial about how to make your own plugin, I decided to show how easy it is to grab and experiment with existing plugins.

Installing krew

If you haven’t heard about it yet, Krew is a new tool released by the Google Container Tools team for managing Kubernetes plugins. As far as I know this is the first plugin manager offering available, and it really scratches my itch for finding a specific tool for a specific job (while also being easy to use).

Krew basically builds on top of the kubectl plugin architecture for making it easier to deal with plugins by providing a sort of framework for keeping track of things and making sure they are doing what they are supposed to.

The following kubectl-compatible plugins are available:

/home/jmreicha/.krew/bin/kubectl-krew
/home/jmreicha/.krew/bin/kubectl-rbac_lookup
...

You can manage plugins without Krew, but if you work with a lot of plugins complexity and maintenance generally start to escalate quickly if you are managing everything manually. Below I will show you how easy it is to deal with plugins instead using Krew.

There are installation instructions in the repo, but it is really easy to get going. Run the following commands in your shell and you are ready to go.

(
  set -x; cd "$(mktemp -d)" &&
  curl -fsSLO "https://storage.googleapis.com/krew/v0.2.1/krew.{tar.gz,yaml}" &&
  tar zxvf krew.tar.gz &&
  ./krew-"$(uname | tr '[:upper:]' '[:lower:]')_amd64" install \
    --manifest=krew.yaml --archive=krew.tar.gz
)

# Then append the following to your .zshrc or bashrc
export PATH="${KREW_ROOT:-$HOME/.krew}/bin:$PATH"

# Then source your shell to pick up the path
source ~/.zshrc # or ~/.bashrc

You can use the kubectl plugin list command to look at all of your plugins.

Test it out to make sure it works.

kubectl krew help

If everything went smoothly you should see some help information and can start working with the plugin manager. For example, if you want to check currently available plugins you can use Krew.

kubectl krew update
kubectl krew search

Or you can browse around the plugin index on GitHub. Once you find a plugin you want to try out, just install it.

kubectl krew install view-utilization

That’s it. Krew should take care of downloading the plugin and putting it in the correct path to make it usable right away.

kubectl view-utilization

Some plugins require additional tools to be installed beforehand as dependencies but should tell you which ones are required when they are installed the first time.

Installing plugin: view-secret
CAVEATS:
\
 |  This plugin needs the following programs:
 |  * jq
/
Installed plugin: view-secret

When you are done with a plugin, you can install it just as easily as it was installed.

kubectl krew uninstall view-secret

Conclusion

I must say I am a really big fan of this new model for managing and creating plugins, and I think it will encourage the community to develop even more tools so I’m looking forward to seeing what people come up with.

Likewise I think Krew is a great fit for this because it is super easy to get installed and started with, which I think is important for gaining widespread adoption in the community. If you have an idea for a Kubectl plugin please consider adding it to the krew-index. The project maintainers are super friendly and are great about feedback and getting things merged.

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Kubernetes CLI Tricks

 

Kubernetes is complicated, as you’ve probably already discovered if you’ve used Kubernetes before.  Likewise, the Kubectl command line tool can pretty much do anything but can feel cumbersome, clunky and generally overwhelming for those that are new to the Kubernetes ecosystem.  In this post I want to take some time to describe a few of the CLI tools that I have discovered that help ease the pain of working with and managing Kubernetes from the command line.

There are many more tools out there and the list keeps growing, so I will probably revisit this post in the future to add more cool stuff as the community continues to grow and evolve.

Where to find projects?

As a side note, there are a few places to check for tools and projects.  The first is the CNCF Cloud Native Landscape.  This site aims to keep track of all the various different projects in the Cloud/Kubernetes world.  An entire post could be written about all of the features and and filters but at the highest level it is useful for exploring and discovering all the different evolving projects.  Make sure to check out the filtering capabilities.

The other project I have found to be extremely useful for finding different projects is the awesome-kubernetes repo on Github.  I found a number of tools mentioned in this post because of the awesome-kubernetes project.  There is some overlap between the Cloud Native Landscape and awesome-kubernetes but they mostly compliment each other very nicely.  For example, awesome-kubernetes has a lot more resources for working with Kubernetes and a lot of the smalller projects and utilities that haven’t made it into the Cloud Native Landscape.  Definitely check this project out if you’re looking to explore more of the Kubernetes ecosystem.

Kubectl tricks

These are various little tidbits that I have found to help boost my productivity from the CLI.

Tab completion – The first thing you will probably want to get working when starting.  There are just too many options to memorize and tab completion provides a nice way to look through all of the various commands when learning how Kubernetes works.  To install (on OS X) run the following command.

brew install bash-completion

In zsh, adding the completion is as simple as running source <(kubectl completion bash).  The same behavior can be accomplished in zsh using source <(kubectl completion zsh).

Aliases and shortcuts – One distinct flavor of Kubernetes is how cumbersome the CLI can be.  If you use Zsh and something like oh-my-zsh, there is a default set of aliases that work pretty well, which you can find here.  There are a many posts about aliases out there already so I won’t go into too much detail about them.  I will say though that aliasing k to kubectl is one of the best time savers I have found so far.  Just add the following snippet to your bash/zsh profile for maximum glory.

alias k=kubectl

kubectl –export – This is a nice hidden feature that basically allows users to switch Kubernetes from imperative (create) to declarative (apply).  The --export flag will basically take an existing object and strip out unwanted/unneeded metadata like statuses and timestamps and present a clear version of what’s running, which can then be exported to a file and applied to the cluster.  The biggest advantage of using declarative configs is the ability to mange and maintain them in git repos.

kubectl top – In newer versions, there is the top command, which gives a high level overview of CPU and memory utilization in the cluster.  Utilization can be filtered at the node level as well as the pod level to give a very quick and dirty view into potential bottlenecks in the cluster.  In older versions, Heapster needs to be installed for this functionaliity to work correctly, and in newer versions needs metrics-server to be running.

kubectl explain – This is a utility built in to Kubectl that basically provides a man page for what each Kubernetes resource does.  It is a simple way to explore Kubernetes without leaving the terminal

kubectx/kubens

This is an amazing little utility for quickly moving between Kubernetes contexts and namespaces.  Once you start working with multiple different Kubernetes clusters, you notice how cumbersome it is to switch between environments and namespaces.  Kubectx solves this problem by providing a quick and easy way to see what environments and namespaces a user is currently in and also quickly switch between them.  I haven’t had any issues with this tool and it is quickly becoming one of my favorites.

stern

Dealing with log output using Kubectl is a bit of a chore.  Stern (and similarly kail) offer a much nicer user experience when dealing with logs.  These tools allow users the ability to do things like show logs for multiple containers in pod,  use regex matching to tail logs for specific containers, give nice colored output for distinguishing between logs, filter logs by namespaces and a bunch of other nice features.

Obviously for a full setup, using an aggregated/centralized logging solution with something like Fluenctd or Logstash would be more ideal, but for examining logs in a pinch, these tools do a great job and are among my favorites.  As an added bonus, I don’t have to copy/paste log names any more.

yq

yq is a nice little command line tool for parsing yaml files, which works in a similar way to the venerable jq.  Parsing, reading, updating yaml can sometimes be tricky and this tool is a great and lightweight way to manipulate configurations.  This tool is especially useful for things like CI/CD where a tag or version might change that is nested deep inside yaml.

There is also the lesser known jsonpath option that allows you to interact with the json version of a Kubernetes object, baked into kubectl.  This feature is definitely less powerful than jq/yq but works well when you don’t want to overcomplicate things.  Below you can see we can use it to quickly grab the name of an object.

kubectl get pods -o=jsonpath='{.items[0].metadata.name}'

Working with yaml and json for configuration in general seems to be an emerging pattern for almost all of the new projects.  It is definitely worth learning a few tools like yq and jq to get better at parsing and manipulating data using these tools.

ksonnet / jsonnet

Similar to the above, ksonnet and jsonnet are basically templating tools for working with Kubernetes and json objects.  These two tools work nicely for managing Kubernetes manifests and make a great fit for automating deployments, etc. with CI/CD.

ksonnet and jsonnet are gaining popularity because of their ease of use and simplicity compared to a tool like Helm, which also does templating but needs a system level permission pod running in the Kubernetes cluster.  Jsonnet is all client side, which removes the added attack vector but still provides users with a lot of flexibility for creating and managing configs that a templating language provides.

More random Kubernetes tricks

Since 1.10, kubectl has the ability to port forward to resource name rather than just a pod.  So instead of looking up pods that are running and connecting to one all the time, you can just grab the service name or deployment and just port forward to it.

port-forward TYPE/NAME [LOCAL_PORT:]REMOTE_PORT
k port-forward deployment/mydeployment 5000:6000

New in 1.11, which will be dropping soonish, there is a top level command called api-resource, which allows users to view and interact with API objects.  This will be a nice troubleshooting tool to have if for example you are wanting to see what kinds of objects are in a namespace.  The following command will show you these objects.

k api-resources --verbs=list --namespace -o name | xargs -n 1 kubectl get -o name -n foo

Another handy trick is the ability to grab a base64 string and decode it on the fly.  This is useful when you are working with secrets and need to quickly look at what’s in the secret.  You can adapt the following command to accomplish this (make sure you have jq installed).

k get secret my-secret --namespace default -o json | jq -r '.data | .["secret-field"]' | base64 --decode

Just replace .["secret-field"] to use your own field.

UPDATE: I just recently discovered a simple command line tool for decoding base64 on the fly called Kubernetes Secret Decode (ksd for short).  This tool looks for base64 and renders it out for you automatically so you don’t have to worry about screwing around with jq and base64 to extract data out when you want to look at a secret.

k get secret my-secret --namespace default -o json | ksd

That command is much cleaner and easier to use.  This utility is a Go app and there are binaries for it on the releases page, just download it and put it in your path and you are good to go.

Conclusion

The Kubernetes ecosystem is a vast world, and it only continues to grow and evolve.  There are many more kubectl use cases and community to tools that I haven’t discovered yet.  Feel free to let me know any other kubectl tricks you know of, and I will update them here.

I would love to grow this list over time as I get more acquainted with Kubernetes and its different tools.

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