Debugging Kubernetes Apps with kubectl debug
Published: 2023-11-21 05:43:02

## What Is the kubectl debug Command? 

The `kubectl debug` command is a tool provided by Kubernetes, as part of the [kubectl command line](https://komodor.com/learn/the-ultimate-kubectl-cheat-sheet/), to help developers debug their applications running in Kubernetes clusters. It's a powerful command that allows you to run a new container for debugging in the context of an existing pod, without disrupting the running application.

The `kubectl debug` command was introduced as an alpha feature in Kubernetes 1.18 and became beta in Kubernetes 1.20. It's a part of the `kubectl` command-line interface (CLI), which is a versatile tool used to manage Kubernetes clusters. It includes numerous commands that help developers interact with Kubernetes, and `kubectl debug` is one of the most powerful among them.

The `kubectl debug` command is a [Kubernetes troubleshooting solution](https://komodor.com/learn/kubernetes-troubleshooting-the-complete-guide/) that is easy to use, flexible, and efficient. It offers a command-line interface for debugging that is straightforward and user-friendly, making it easy for developers to navigate through their Kubernetes applications and identify issues. The `kubectl debug` command is especially useful for debugging complex microservices architectures where multiple services are running in the same pod.


## kubectl debug: Syntax and Command Structure

The `kubectl debug` command uses the following syntax: 


```
kubectl debug (POD | TYPE/NAME) --image=image [--] [args...]
```


In this syntax:



* `(POD | TYPE/NAME)` specifies the name of the pod or the type and name of the resource to debug.
* `--image=image` specifies the container image to use for the debug container.
* `[args...]` are optional arguments that can be passed to the command.

This syntax allows you to debug a specific container in a multi-container pod or even debug a specific process within a container.


## How kubectl debug Enhances Traditional Kubernetes Debugging Methods [SQ]

Traditional Kubernetes debugging methods often involve checking the logs of the application, describing the pod, or executing a command in the pod. While these methods are useful, they are often not sufficient for complex debugging scenarios. In contrast, `kubectl debug` provides a more hands-on approach.

With `kubectl debug`, you can create a temporary container in the same pod, with the same configuration and in the same namespace as the application you're debugging. This allows you to have a complete view of the application and its environment, making it easier to identify and troubleshoot issues.

Moreover, `kubectl debug` allows you to use any container image for debugging. This means you can use a container image that includes the debugging tools you need, which may not be included in the application's container image. This is especially useful when debugging complex applications that require specialized debugging tools.


## Use Cases for kubectl debug [SQ]

The `kubectl debug` command can be used in a variety of scenarios to debug Kubernetes applications. Here are a few examples:


### Troubleshooting Application Failures

One of the most common use cases for `kubectl debug` is troubleshooting application failures. If your application is crashing or not behaving as expected, you can use `kubectl debug` to create a debug container and investigate the issue.

With `kubectl debug`, you can inspect the application's environment, check the file system, examine network settings, and use debugging tools to analyze the application's behavior. This can help you identify the root cause of the problem and fix it.


### Finding Security Issues

Another use case for `kubectl debug` is [finding Kubernetes security issues](https://www.tigera.io/learn/guides/kubernetes-security/). Kubernetes applications can sometimes be vulnerable to security issues, and `kubectl debug` can help you identify and mitigate these vulnerabilities.

By creating a debug container with `kubectl debug`, you can inspect the application's environment and configuration, check for insecure settings, and use security tools to analyze the application for vulnerabilities. This can help you improve the security of your Kubernetes applications.


### Resource and Performance Analysis

Finally, `kubectl debug` can be used for resource and performance analysis. Kubernetes applications can sometimes be resource-intensive or have performance issues, and `kubectl debug` can help you identify and mitigate these issues.

With `kubectl debug`, you can monitor the resource usage of the application, analyze its performance, and identify bottlenecks. This can help you optimize your Kubernetes applications and improve their performance and resource efficiency.


## Best Practices in Kubernetes Debugging with kubectl 


### Check Logs First

Logs can provide valuable insights into what might be causing an issue. For instance, they might show error messages or tracebacks related to a problem, or they might reveal patterns of behavior that could give clues as to the cause of an issue.

To check the logs of a particular pod, you can use the `kubectl logs` command followed by the pod's name. This will display the logs of the pod's main container. If the pod has multiple containers, you can specify the container's name using the `-c` or `--container` option.


### Inspect Pod and System Status

Inspecting the status of the pod and the system as a whole can help identify whether the problem is isolated to a particular pod or if it's affecting the entire system.

To inspect the status of a pod, you can use the `kubectl describe pod` command followed by the pod's name. This will provide detailed information about the pod, including its current status, recent events, and any error messages.

Inspecting the system status involves checking the status of all pods in the Kubernetes cluster. You can do this using the `kubectl get pods` command, which will display a list of all pods along with their current status.


### Use Labels and Selectors for Filtering

Another useful practice when debugging Kubernetes applications is to use labels and selectors for filtering. This can make it easier to focus on specific pods or sets of pods that are relevant to the issue you're trying to solve.

Labels are key-value pairs that you can attach to Kubernetes objects, including pods. They can be used to organize and select subsets of objects. For example, you might label all pods belonging to a particular application with the same label, making it easier to manage and debug them as a group.

Selectors are expressions that match certain labels. You can use selectors with various `kubectl` commands to filter the objects that the commands apply to. For example, the `kubectl get pods -l app=myapp` command will display only the pods labeled with `app=myapp`.


### Check the Security Contexts and Permissions

Finally, it's also important to check the security contexts and permissions of your Kubernetes objects. Misconfigured security settings can often be the cause of problems in Kubernetes applications.

Security contexts define the security settings for a pod or a container. They can control various aspects of a container's security, such as whether it runs as a privileged container, its Linux capabilities, and much more. You can check a pod's or a container's security context using the `kubectl describe pod` command.

Permissions, on the other hand, govern what operations a user or a service account can perform on Kubernetes objects. Misconfigured permissions can prevent your application from functioning correctly. You can check the permissions of a user or a service account using the `kubectl auth can-i` command.

By incorporating these best practices into your debugging process, you can streamline the troubleshooting of your Kubernetes applications and ensure their smooth and reliable operation.