How to use docker scout cache prune command to manage cache

Introduction

In this lab, you will learn how to manage the cache used by the docker scout command. As docker scout analyzes images, it caches data like SBOMs and vulnerability information to improve performance. Over time, this cache can consume significant disk space.

You will explore the docker scout cache prune command and its options. Specifically, you will learn how to prune temporary data, how to prune both temporary data and cached SBOMs, and how to force the pruning process without confirmation. By the end of this lab, you will be able to effectively manage the docker scout cache to free up disk space and ensure you are working with fresh data when needed.

Skills Graph

%%%%{init: {'theme':'neutral'}}%%%% flowchart RL docker(("Docker")) -.-> docker/ImageOperationsGroup(["Image Operations"]) docker(("Docker")) -.-> docker/SystemManagementGroup(["System Management"]) docker/ImageOperationsGroup -.-> docker/pull("Pull Image from Repository") docker/SystemManagementGroup -.-> docker/prune("Remove Unused Docker Objects") subgraph Lab Skills docker/pull -.-> lab-555199{{"How to use docker scout cache prune command to manage cache"}} docker/prune -.-> lab-555199{{"How to use docker scout cache prune command to manage cache"}} end

Understand the purpose of docker scout cache prune

In this step, we will understand the purpose of the docker scout cache prune command.

As you use docker scout to analyze images, it caches data like Software Bill of Materials (SBOMs) and vulnerability information to speed up subsequent analyses. Over time, this cache can grow large and consume significant disk space. The docker scout cache prune command is used to remove this cached data.

Think of it like clearing your web browser's cache. Just as clearing your browser cache can free up space and sometimes resolve issues, pruning the Docker Scout cache can free up disk space and ensure you are working with fresh data if needed.

The docker scout cache prune command provides options to control what data is removed. By default, it removes temporary data. You can also choose to remove cached SBOMs.

We will explore these options in the following steps. For now, let's just understand that this command is a maintenance tool to manage the data cached by docker scout.

Prune temporary data using docker scout cache prune

In this step, we will prune temporary data using the docker scout cache prune command.

Before pruning, let's simulate some docker scout activity to ensure there is data to prune. We will analyze a simple image.

First, pull a small image to work with.

docker pull hello-world

You should see output indicating the image was pulled successfully.

Now, let's run a docker scout analysis on this image.

docker scout cves hello-world

This command analyzes the hello-world image for Common Vulnerabilities and Exposures (CVEs). Even though hello-world is a very simple image and likely has no vulnerabilities, this command will still generate and cache some temporary data related to the analysis process.

You will see output showing the analysis results (likely indicating no vulnerabilities found).

Now, let's prune the temporary cache data. Run the docker scout cache prune command without any additional flags.

docker scout cache prune

When you run this command, you will be prompted to confirm the action. This is a safety measure to prevent accidental data loss.

WARNING! This will remove all temporary cache data. Are you sure you want to continue? [y/N]

Type y and press Enter to confirm.

You should see output indicating that temporary cache data has been pruned and the amount of space reclaimed. The exact output may vary depending on the amount of temporary data that was cached.

This command specifically targets temporary files and data generated during docker scout operations, helping to keep your cache clean without removing more persistent data like cached SBOMs (which we will cover in the next step).

Prune temporary data and cached SBOMs using docker scout cache prune --sboms

In this step, we will prune both temporary data and cached SBOMs using the docker scout cache prune --sboms command.

In the previous step, we pruned only temporary data. Cached SBOMs are more persistent data generated when docker scout analyzes an image to create a Software Bill of Materials. Keeping cached SBOMs can speed up future analyses of the same image, but they also consume disk space.

To demonstrate pruning SBOMs, let's first analyze an image to generate an SBOM. We'll use the ubuntu image for this.

docker pull ubuntu

This command pulls the ubuntu image.

Now, let's generate and cache the SBOM for the ubuntu image.

docker scout sbom ubuntu

This command generates the SBOM for the ubuntu image and caches it. You will see the SBOM output in your terminal.

Now, let's prune both temporary data and cached SBOMs. We will use the --sboms flag with the docker scout cache prune command.

docker scout cache prune --sboms

Again, you will be prompted to confirm the action. This time, the warning will indicate that both temporary data and cached SBOMs will be removed.

WARNING! This will remove all temporary cache data and cached SBOMs. Are you sure you want to continue? [y/N]

Type y and press Enter to confirm.

You should see output indicating that temporary cache data and cached SBOMs have been pruned, along with the amount of space reclaimed. The space reclaimed should be larger than in the previous step because cached SBOMs were also removed.

Using the --sboms flag gives you more aggressive cache cleaning, which is useful when you need to free up more disk space or if you suspect issues with cached SBOM data.

Force prune without confirmation using docker scout cache prune --force

In this step, we will learn how to force the pruning of the Docker Scout cache without being prompted for confirmation, using the --force flag.

By default, docker scout cache prune requires user confirmation to prevent accidental data deletion. However, in automated scripts or situations where you are certain you want to prune the cache, the --force flag can be used to skip the confirmation prompt.

Let's first generate some cache data again. We'll analyze the alpine image this time.

docker pull alpine

This command pulls the alpine image.

Now, let's run a docker scout analysis on this image to generate some cache data.

docker scout cves alpine

This analyzes the alpine image for CVEs and caches the results.

Now, we will prune the cache using the --force flag. We will also include the --sboms flag to prune both temporary data and cached SBOMs, as this is a common use case for forced pruning.

docker scout cache prune --sboms --force

Notice that this time, you are not prompted to confirm the action. The command executes immediately and prunes the specified cache data.

You should see output indicating that temporary cache data and cached SBOMs have been pruned, similar to the previous step, but without the interactive prompt.

Using --force should be done with caution, as it bypasses the safety confirmation. It is best used in non-interactive environments or when you are absolutely sure about the pruning operation.

Summary

In this lab, we learned the purpose of the docker scout cache prune command, which is used to manage the cache data generated by docker scout analyses, such as SBOMs and vulnerability information. This command helps free up disk space and ensures you are working with fresh data when needed.

We then practiced using the command to prune temporary data generated by a docker scout cves analysis on the hello-world image. We also explored the --sboms flag to prune both temporary data and cached SBOMs, and the --force flag to bypass the confirmation prompt during pruning.