Fix: Java 17 Issue On Raspberry Pi With Java 21

Nov 25, 2025 by Alex Johnson 48 views

Fixing Java 17 Issue on Raspberry Pi with Java 21

Experiencing build failures on your Raspberry Pi due to the deprecation of Java 17 and the current Java 21 version? You're not alone! This comprehensive guide provides a step-by-step workaround to get your system running smoothly again. This article provides a workaround solution for resolving script failures on Raspberry Pi caused by the transition from Java 17 to Java 21. This involves creating a dummy Java 17 environment while ensuring Java 21 is correctly installed and utilized.

Understanding the Problem

The core issue arises when software or scripts require Java 17, but the system has been updated to Java 21. This incompatibility can lead to build failures and other operational problems. The solution involves creating a "dummy" Java 17 environment that satisfies the dependency requirements of older software while still leveraging the benefits of Java 21.

Why This Happens

As technology evolves, software dependencies can become a hurdle. In this case, certain applications or scripts might explicitly require Java 17. When a system is upgraded to Java 21, these dependencies aren't automatically resolved. The dummy package tricks the system into thinking Java 17 is present, while Java 21 handles the actual execution.

Key Benefits of This Approach

Maintain Compatibility: Ensures older applications that depend on Java 17 continue to function.
Leverage Java 21: Allows you to take advantage of the performance improvements and new features in Java 21.
Clean Solution: Avoids downgrading the entire system to Java 17, which can introduce other issues.

Workaround Steps

Here’s a detailed guide to creating a dummy Java 17 environment and ensuring Java 21 is correctly installed and utilized on your Raspberry Pi.

Step 1: Optional Clean Up

Before starting, it's a good practice to clean up any previous dummy packages that might interfere with the new setup. This ensures a clean slate and avoids potential conflicts.

for PKG in openjdk-17-jdk-fake fake-openjdk17; do
  if dpkg -s "$PKG" >/dev/null 2>&1; then
    echo "Removing old dummy package: $PKG"
    sudo dpkg -r "$PKG"
  fi
done

This script iterates through potential dummy package names (openjdk-17-jdk-fake and fake-openjdk17). For each package, it checks if it's installed using dpkg -s. If the package is found, the script removes it using sudo dpkg -r. The >/dev/null 2>&1 part suppresses any output from the dpkg -s command, keeping the terminal clean unless a package is actually removed.

Step 2: Install Java 21 and Equivs

Next, install the real Java 21 along with equivs. Equivs is a tool that allows you to create Debian packages that declare dependencies and provide virtual packages. This is crucial for creating our dummy Java 17 package.

sudo apt update
sudo apt install -y openjdk-21-jdk openjdk-21-jre equivs

sudo apt update: Refreshes the package lists, ensuring you have the latest versions available.
sudo apt install -y openjdk-21-jdk openjdk-21-jre equivs: Installs the Java Development Kit (JDK) and Java Runtime Environment (JRE) for Java 21, as well as the equivs tool. The -y flag automatically answers "yes" to any prompts, making the installation non-interactive.

After installation, verify that Java 21 is correctly installed by checking the Java version.

java -version

You should see output confirming that Java 21 is installed and running.

Step 3: Create a Dummy Package

Now, create a dummy package that provides openjdk-17-jdk but depends on openjdk-21-jdk. This is where the magic happens. The dummy package will satisfy the dependency requirements of applications needing Java 17, while Java 21 handles the actual execution.

First, create a directory for the dummy package and navigate into it:

mkdir -p ~/fake-openjdk17
cd ~/fake-openjdk17

Then, create a file named openjdk-17-jdk-fake with the following content:

cat > openjdk-17-jdk-fake << 'EOF'
Section: misc
Priority: optional
Standards-Version: 4.5.0

Package: openjdk-17-jdk-fake
Version: 17.0-1
Maintainer: Fake Java <root@localhost>
Architecture: all
Depends: openjdk-21-jdk
Provides: openjdk-17-jdk
Description: Dummy package that provides openjdk-17-jdk but uses openjdk-21-jdk
 This meta package is only to satisfy packages that require openjdk-17-jdk.
EOF

Let's break down this file:

Section: misc: Categorizes the package as miscellaneous.
Priority: optional: Sets the priority of the package as optional.
Standards-Version: 4.5.0: Specifies the Debian standards version.
Package: openjdk-17-jdk-fake: The name of the dummy package.
Version: 17.0-1: The version number of the dummy package.
Maintainer: Fake Java <root@localhost>: The maintainer information.
Architecture: all: Indicates the package is architecture-independent.
Depends: openjdk-21-jdk: Specifies that this package depends on openjdk-21-jdk. This ensures Java 21 is installed.
Provides: openjdk-17-jdk: Declares that this package provides openjdk-17-jdk. This is the key part that satisfies the dependency requirements of other software.
Description: A brief description of the package.

Next, build and install the dummy package using equivs-build:

equivs-build openjdk-17-jdk-fake

This command generates a .deb package file. Now, install the dummy package:

sudo dpkg -i openjdk-17-jdk-fake_17.0-1_all.deb

This command installs the dummy package, making the system think Java 17 is present.

Step 4: Ensure Java Points to 21

If you have multiple Java versions installed, you need to ensure that the system default Java version points to Java 21. This can be done using the update-alternatives command.

sudo update-alternatives --config java

This command will present a list of installed Java versions. Select the number corresponding to Java 21 to make it the default.

Final Check

Finally, verify that the setup is correct by checking the Java version again:

java -version

If you see Java 21 in the output, you have successfully created the dummy Java 17 environment while running Java 21.

echo "If you see Java 21 here, you are good to go."

Troubleshooting

Package Dependency Issues

If you encounter issues with package dependencies, ensure that you have run sudo apt update before installing any packages. This updates the package lists and resolves dependency conflicts.

Java Version Not Correct

If the java -version command does not show Java 21 after the setup, double-check that you have correctly configured the alternatives using sudo update-alternatives --config java.

Dummy Package Installation Failed

If the dummy package installation fails, ensure that you have correctly created the openjdk-17-jdk-fake file and that the equivs tool is properly installed.

Conclusion

By following these steps, you can effectively resolve the Java 17 issue on Raspberry Pi while continuing to use Java 21. This ensures that your applications and scripts that require Java 17 will run smoothly, and you can leverage the latest Java features and performance improvements. This workaround is particularly useful for systems that have upgraded to Java 21 but still need to support older software with Java 17 dependencies. Remember to regularly check for updates and consider migrating applications to newer Java versions to avoid future compatibility issues.

For more information on Java and Raspberry Pi, you can visit the official Oracle Java Documentation.