How to set JAVA_HOME in Linux for all users

Setting the JAVA_HOME environment variable for all users in Linux typically requires system-level configuration to ensure that all current and new user sessions can access the JAVA_HOME variable. The following is a clear step-by-step solution:

1. Installing Java

   First, ensure that Java is installed. You can install Java using the command line; for example, on Ubuntu, use the following command:

   bash
   sudo apt update
   sudo apt install openjdk-11-jdk

2. Locating the Java Installation Path

   After installing Java, find the Java installation path. This can be done by running the following command:

   bash
   update-alternatives --config java

   This command lists all installed Java versions and their paths. Select the version you want to set as JAVA_HOME.

3. Setting JAVA_HOME

   Once you know the Java installation path, set JAVA_HOME for all users. In Linux, configure this variable in the /etc/environment file to affect all users. To do this, edit the file with superuser privileges using a text editor, as follows:

   bash
   sudo nano /etc/environment

   In the opened file, add the following line (replace <JAVA_PATH> with the actual Java path from the previous step and ensure you do not include bin/java):

   plaintext
   JAVA_HOME="<JAVA_PATH>"

   For example, if your Java path is /usr/lib/jvm/java-11-openjdk-amd64, add:

   plaintext
   JAVA_HOME="/usr/lib/jvm/java-11-openjdk-amd64"

   Save and close the file.

4. Making the Variable Effective

   To apply the changes, ask users to log out and log back in, or run the following command to make the /etc/environment changes effective immediately:

   bash
   source /etc/environment

   Alternatively, for the current session, manually export the variable:

   bash
   export JAVA_HOME="/usr/lib/jvm/java-11-openjdk-amd64"

5. Verifying JAVA_HOME Setup

   To verify that JAVA_HOME is correctly set, run the following command in any user's session:

   bash
   echo $JAVA_HOME

   If set correctly, it should output the Java path you previously configured.

By following these steps, the JAVA_HOME environment variable will be added to the system's global environment, so all users will have this variable set in their sessions. This is very useful when installing software that requires a Java runtime environment, such as Apache Tomcat or Maven.