JAVA_HOME is the single environment variable that every Java tool checks first. Tomcat, Maven, Gradle, Elasticsearch, Jenkins, and dozens of other applications use it to locate the JDK. When it is wrong or missing, you get cryptic errors about missing tools or wrong Java versions. When multiple JDK versions are installed on the same system (which is common on build servers), getting JAVA_HOME right becomes even more important.
This guide covers every method for setting JAVA_HOME on Rocky Linux, AlmaLinux, RHEL 10, and Fedora 42: the alternatives system for switching the system default, /etc/profile.d/ for system-wide persistence, ~/.bashrc for per-user settings, systemd unit overrides for services, and a dynamic approach that follows alternatives automatically. All commands were tested with OpenJDK 21 and 25 on Rocky Linux 10 and Fedora 42.
Verified working: March 2026 on Rocky Linux 10.1 (kernel 6.12), Fedora 42 with OpenJDK 21.0.10, OpenJDK 25.0.2
Prerequisites
- Rocky Linux 10 / AlmaLinux 10 / RHEL 10 or Fedora 42
- At least one JDK installed (not just JRE). Install it with:
sudo dnf install -y java-21-openjdk-develFor a second JDK version (to practice switching):
sudo dnf install -y java-25-openjdk-develVerify both are installed:
ls -d /usr/lib/jvm/java-*-openjdkYou should see both JDK directories:
/usr/lib/jvm/java-21-openjdk
/usr/lib/jvm/java-25-openjdkFind Where Java Is Installed
Before setting JAVA_HOME, you need to know the actual installation path. There are three quick ways to find it.
Follow the symlink chain from the java binary:
readlink -f $(which java)This resolves all symlinks and returns the real path:
/usr/lib/jvm/java-21-openjdk/bin/javaJAVA_HOME is the directory two levels up from the binary, so in this case: /usr/lib/jvm/java-21-openjdk.
You can also ask Java directly for its home directory:
java -XshowSettings:properties 2>&1 | grep java.homeOutput:
java.home = /usr/lib/jvm/java-21-openjdkSwitch the System Default with alternatives
The alternatives system manages symlinks for commands that have multiple providers. When you install two JDK versions, alternatives controls which one /usr/bin/java points to.
List all installed Java versions:
sudo alternatives --config javaThe output lists each installed JDK with a selection number:
There are 2 programs which provide 'java'.
Selection Command
-----------------------------------------------
*+ 1 /usr/lib/jvm/java-21-openjdk/bin/java
2 /usr/lib/jvm/java-25-openjdk/bin/java
Enter to keep the current selection[+], or type selection number:Type 2 and press Enter to switch to Java 25. The * marks the current default, and + marks the auto-selected option (highest priority).
To switch non-interactively (useful in scripts and automation):
sudo alternatives --set java /usr/lib/jvm/java-25-openjdk/bin/java
sudo alternatives --set javac /usr/lib/jvm/java-25-openjdk/bin/javacVerify the switch:
java -versionConfirms Java 25 is now active:
openjdk version "25.0.2" 2026-01-20 LTS
OpenJDK Runtime Environment (Red_Hat-25.0.2.0.10-3) (build 25.0.2+10-LTS)
OpenJDK 64-Bit Server VM (Red_Hat-25.0.2.0.10-3) (build 25.0.2+10-LTS, mixed mode, sharing)Remember to switch both java and javac. They are managed as separate alternatives. If you switch only java, the compiler might still point to the old version.
Set JAVA_HOME System-Wide
The alternatives system only changes which java binary the symlink points to. It does not set the JAVA_HOME environment variable. Many applications (Tomcat, Maven, Gradle) require JAVA_HOME to be explicitly set.
Create a shell profile script that sets JAVA_HOME for all users on the system:
echo 'export JAVA_HOME=/usr/lib/jvm/java-21-openjdk' | sudo tee /etc/profile.d/java.sh
echo 'export PATH=$JAVA_HOME/bin:$PATH' | sudo tee -a /etc/profile.d/java.sh
sudo chmod +x /etc/profile.d/java.shVerify the contents:
cat /etc/profile.d/java.shThe file should contain:
export JAVA_HOME=/usr/lib/jvm/java-21-openjdk
export PATH=$JAVA_HOME/bin:$PATHLoad it in the current session (or log out and back in):
source /etc/profile.d/java.sh
echo $JAVA_HOMEOutput:
/usr/lib/jvm/java-21-openjdkThis approach pins JAVA_HOME to a specific version. When you want to switch versions, update both alternatives and the /etc/profile.d/java.sh file.
Dynamic JAVA_HOME That Follows alternatives
If you switch Java versions frequently, maintaining a static path in /etc/profile.d/java.sh gets tedious. A dynamic approach resolves JAVA_HOME from the current alternatives selection every time a shell starts:
echo 'export JAVA_HOME=$(dirname $(dirname $(readlink -f $(which java))))' | sudo tee /etc/profile.d/java.sh
sudo chmod +x /etc/profile.d/java.shThis command reads the java symlink, resolves it to the real path, strips /bin/java from the end, and exports the result. When you switch alternatives, JAVA_HOME follows automatically in new shell sessions.
Verify it works after switching alternatives:
sudo alternatives --set java /usr/lib/jvm/java-25-openjdk/bin/java
source /etc/profile.d/java.sh
echo $JAVA_HOMEJAVA_HOME now points to Java 25 without editing any files:
/usr/lib/jvm/java-25-openjdkPer-User JAVA_HOME
If different users on the same system need different Java versions (common on shared build servers), set JAVA_HOME in the user’s ~/.bashrc:
echo 'export JAVA_HOME=/usr/lib/jvm/java-25-openjdk' >> ~/.bashrc
echo 'export PATH=$JAVA_HOME/bin:$PATH' >> ~/.bashrc
source ~/.bashrcThis overrides the system-wide setting from /etc/profile.d/java.sh for that specific user. The per-user PATH takes precedence, so even if alternatives points to Java 21, this user runs Java 25.
Set JAVA_HOME for systemd Services
Services managed by systemd (like Tomcat, Elasticsearch, Jenkins) do not read shell profiles. They run in an isolated environment where /etc/profile.d/ scripts have no effect. You must set JAVA_HOME directly in the service unit file.
The cleanest approach is a drop-in override that survives package updates:
sudo systemctl edit tomcatAdd the following between the comment markers:
[Service]
Environment="JAVA_HOME=/usr/lib/jvm/java-21-openjdk"Save and close. Then reload and restart the service:
sudo systemctl daemon-reload
sudo systemctl restart tomcatThis creates a file at /etc/systemd/system/tomcat.service.d/override.conf that persists across package updates. If you edit the main unit file directly, your changes get overwritten when the package updates.
You can also set the environment in a dedicated file referenced by the unit:
echo "JAVA_HOME=/usr/lib/jvm/java-21-openjdk" | sudo tee /etc/sysconfig/tomcatThen reference it in the service unit with EnvironmentFile=/etc/sysconfig/tomcat. Many RHEL-family packages already use /etc/sysconfig/ for this purpose.
Which Applications Need JAVA_HOME?
Not every Java application requires JAVA_HOME, but these do:
| Application | How it uses JAVA_HOME |
|---|---|
| Apache Maven | Checks $JAVA_HOME first, falls back to $(which java) |
| Gradle | Uses $JAVA_HOME or org.gradle.java.home in properties |
| Apache Tomcat | Reads $JAVA_HOME in catalina.sh or systemd environment |
| Elasticsearch | Uses $JAVA_HOME if set, otherwise its bundled JDK |
| Jenkins | Needs $JAVA_HOME in systemd unit or /etc/sysconfig/jenkins |
| Hadoop / Spark | Requires $JAVA_HOME in hadoop-env.sh / spark-env.sh |
| Android SDK | Uses $JAVA_HOME for sdkmanager and build tools |
Common Mistakes
A few traps that catch people regularly:
- Setting JAVA_HOME to the bin directory:
JAVA_HOME=/usr/lib/jvm/java-21-openjdk/binis wrong. Tools append/bin/javato JAVA_HOME, so they end up looking for/bin/bin/java. The correct value has no trailing/bin - Switching alternatives but not JAVA_HOME: if you switch
alternativesto Java 25 but JAVA_HOME still points tojava-21-openjdk, Maven and Tomcat will use Java 21 while the command line uses Java 25. Use the dynamic approach or update both together - Setting CLASSPATH with jre/lib: older guides show
export CLASSPATH=$JAVA_HOME/jre/lib. Thejre/subdirectory was removed in JDK 9. Modern JDKs (17, 21, 25) do not have it. Setting CLASSPATH is rarely needed anyway - Forgetting
javacalternatives:alternatives --config javaonly switches the runtime. Runalternatives --config javacseparately or use--setfor both - Expecting systemd to read shell profiles: services started by systemd do not source
/etc/profile.d/or~/.bashrc. UseEnvironment=in the unit file instead
Quick Reference
| Task | Command |
|---|---|
| Find JAVA_HOME | dirname $(dirname $(readlink -f $(which java))) |
| List installed JDKs | ls -d /usr/lib/jvm/java-*-openjdk |
| Switch system default | sudo alternatives --config java |
| Switch non-interactively | sudo alternatives --set java /usr/lib/jvm/java-25-openjdk/bin/java |
| Set system-wide | echo 'export JAVA_HOME=...' | sudo tee /etc/profile.d/java.sh |
| Set per-user | Add export JAVA_HOME=... to ~/.bashrc |
| Set for systemd service | sudo systemctl edit servicename → Environment="JAVA_HOME=..." |
| Verify | echo $JAVA_HOME && java -version |
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