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How a Large Administrator Profile Can Drastically Slow Down EC2 Image Provisioning

Published on 10.12.2025

When working with Amazon EC2 instances, provisioning an image can sometimes take longer than expected, especially when using Windows AMIs. One often-overlooked culprit behind slow instance provisioning is the size of the Administrator profile. In this post, we’ll explore how a large Administrator user directory can slow down the Sysprepprocess during image creation and how you can mitigate these issues to speed up your EC2 provisioning.

Understanding the Role of the Administrator Profile in EC2 Image Provisioning

When you create a custom AMI from a Windows instance, the Sysprep tool is used to generalize the instance. Part of this process involves copying the contents of the Administrator profile to the default profile using the CopyProfile directive. This ensures that any settings or configurations made under the Administrator account are applied to new user accounts created on instances launched from the AMI.

However, if the Administrator profile is large—either due to the number of files, installed applications, or custom configurations—this can significantly slow down the CopyProfile step, leading to long delays during the specializepass of the Sysprep process.

The Impact of a Large Administrator Profile

Recently, we encountered a scenario where the provisioning of a new EC2 instance was taking over 30 minutes to complete. Upon investigation, we discovered that the Administrator profile was approximately 2.7 GB in size and contained numerous files and applications, including Visual Studio Code, Python, and various browsers.

The CopyProfile step, which runs during the Sysprep process, was taking an unusually long time—about 12 minutes—to complete. This was due to the sheer number of files in the Administrator profile that needed to be copied. Each small file and application configuration adds to the time it takes for Sysprep to complete its work, drastically increasing the time required to provision the AMI.

Why Does This Happen?

The CopyProfile directive in Sysprep is designed to copy all user settings, application data, and configurations from the Administrator profile to the default profile. While this is a useful feature when you need to replicate the same environment across new instances, the size and complexity of the profile can greatly affect the time it takes.

Here’s why a large profile can slow down provisioning:

• Number of Files: Even more than the size of the files, the number of individual files and directories in the profile can be a major bottleneck. Copying many small files takes much longer than copying a few large ones, as each file requires its own I/O operation.
• Applications and Dependencies: If you install applications like Visual Studio Code, Python, or browsers for the Administrator account, they often store large amounts of configuration data and cache files in the AppData folder. This data is also copied during the Sysprep process.
• Temporary Files: The Administrator profile often accumulates unnecessary temporary files and logs, which can add to the bulk of the profile and slow down copying.

Diagnosing the Issue

To understand how many files were in the Administrator profile, we used PowerShell to get a count of files in the directory:

Get-ChildItem -Recurse "C:\Users\Administrator" | Where-Object { -not $_.PSIsContainer } | Measure-Object

This command gave us the total file count, which turned out to be in the tens of thousands. Each of these files was being copied during the CopyProfile operation, contributing to the slow image creation.

Solutions to Speed Up Image Provisioning

If you encounter a similar situation where your EC2 instance is taking too long to provision, here are a few ways you can mitigate the problem:

1. Move Applications to a System-Wide Installation

Instead of installing applications like Visual Studio Code, Python, or browsers under the Administrator account, install them system-wide. This moves application files from C:\Users\Administrator\AppData to C:\Program Files, reducing the size of the profile and speeding up the copying process.

2. Clean Up the Administrator Profile

Regularly clean the Administrator profile by:

• Deleting temporary files and logs from C:\Users\Administrator\AppData\Local\Temp.
• Clearing browser caches and unnecessary application data.
• Removing large files or unnecessary applications that don’t need to be replicated to new instances.

3. Disable CopyProfile if Not Needed

If you don’t need to preserve the Administrator profile’s custom settings for new users, you can simply disable the CopyProfile directive in the unattend.xml file. This will eliminate the profile copying step altogether, resulting in much faster provisioning times.

4. Optimize Your AMI

Consider creating a lean AMI where only the necessary applications and settings are included. After instance launch, use AWS Systems Manager (SSM) or other automation tools to install additional software and configurations as needed. This minimizes the size of the base AMI and speeds up the Sysprep process.

Conclusion

A large Administrator profile can severely impact the time it takes to provision an EC2 instance from an AMI, particularly due to the CopyProfile step during the Sysprep process. By cleaning up the profile, moving applications to a system-wide installation, or disabling CopyProfile if unnecessary, you can significantly reduce the time it takes to create new instances.

By following these steps, you can ensure that your EC2 instances provision quickly and efficiently, without being bogged down by excessive profile copying.