How to set JAVA_HOME in Linux for all users

I am new to Linux system and there seem to be too many Java folders.

java -version gives me:

• java version "1.7.0_55"
• OpenJDK Runtime Environment (rhel-2.4.7.1.el6_5-x86_64 u55-b13)
• OpenJDK 64-Bit Server VM (build 24.51-b03, mixed mode)

When I am trying to build a Maven project , I am getting error:

Error: JAVA_HOME is not defined correctly.
We cannot execute /usr/java/jdk1.7.0_05/bin/java

Could you please tell me which files I need to modify for root as well as not-root user and where exactly is java located?

1. find /usr/lib/jvm/java-1.x.x-openjdk

2. vim /etc/profile

   Prepend sudo if logged in as not-privileged user, ie. sudo vim

3. Press 'i' to get in insert mode

4. add:

    export JAVA_HOME="path that you found"
   
    export PATH=$JAVA_HOME/bin:$PATH
   

5. logout and login again, reboot, or use source /etc/profile to apply changes immediately in your current shell

For all users, I would recommend creating a file in /etc/profile.d/java_home.sh the following lines

# Set JDK installation directory according to selected Java compiler

export JAVA_HOME=$(readlink -f /usr/bin/javac | sed "s:/bin/javac::")

This will update dynamically and works well with the alternatives system. Do note though that the update will only take place in a new login shell.

You could use /etc/profile or better a file like /etc/profile.d/jdk_home.sh

export JAVA_HOME=/usr/java/jdk1.7.0_05/

You have to remember that this file is only loaded with new login shells.. So after bash -l or a new gnome-session and that it doesn't change with new Java versions.

None of the other answers were "sticking" for me in RHEL 7, even setting JAVA_HOME and PATH directly in /etc/profile or ~/.bash_profile would not work. Each time I tried to check if JAVA_HOME was set, it would come up blank:

$ echo $JAVA_HOME
    (<-- no output)

What I had to do was set up a script in /etc/profile.d/jdk_home.sh:

#!/bin/sh
export JAVA_HOME=/opt/ibm/java-x86_64-60/
export PATH=$JAVA_HOME/bin:$PATH

I initially neglected the first line (the #!/bin/sh), and it won't work without it.

Now it's working:

$ echo $JAVA_HOME
/opt/ibm/java-x86_64-60/

1. Open terminal and type sudo gedit .bashrc

2. It will ask you your password. After typing the password, it will open the bash file. Then go to end and type:

   export JAVA_HOME="/usr/lib/jvm/java-8-openjdk-amd64/"
   export PATH=$PATH:$JAVA_HOME/bin
   

3. Then save the file and exit from file

Above is for a single user. For all users, you have to follow below steps

1. gedit /etc/profile

2. export JAVA_HOME="/usr/lib/jvm/java-8-openjdk-amd64/"

3. export PATH=$PATH:$JAVA_HOME/bin

Copy the bin file path you installed

YOUR PATH

open terminal and edit environment file by typing following command,

sudo nano /etc/environment

In this file, add the following line (replacing YOUR_PATH by the just copied path):

JAVA_HOME="YOUR_PATH"

That should be enough to set the environment variable. Now reload this file:

source /etc/environment

now test it by executing:

echo $JAVA_HOME

Doing what Oracle does (as a former Sun Employee I can't get used to that one)

ln -s latestJavaRelease /usr/java/default
Where latestJavaRelease is the version that you want to use

then export JAVA_HOME=/usr/java/default

The answer is given previous posts is valid. But not one answer is complete with respect to:

1. Changing the /etc/profile is not recommended simply because of the reason (as stated in /etc/profile):

> * It's NOT a good idea to change this file unless you know what you are doing. It's much better to create a custom.sh shell script in > /etc/profile.d/ to make custom changes to your environment, as this > will prevent the need for merging in future updates.*

2. So as stated above create /etc/profile.d/custom.sh file for custom changes.

3. Now, to always keep updated with newer versions of Java being installed, never put the absolute path, instead use:

> #if making jdk as java home >
> export JAVA_HOME=$(readlink -f /usr/bin/javac | sed "s:/bin/javac::") >
> OR >
> #if making jre as java home >
> export JAVA_HOME=$(readlink -f /usr/bin/java | sed "s:/bin/java::")

4. And remember to have #! /bin/bash on the custom.sh file

First you need to find out which Java is installed in your PC and which one to use. For that open terminal with root permission.

 sudo su

 ls /usr/lib/jvm/

Now it will list the available java versions. Select the listed version.

Copy the path till there.

Now open bashrc

  nano ~/.bashrc

add the following commands to the end

 export JAVA_HOME="path that you copied"

  export PATH=$JAVA_HOME/bin:$PATH

after that save the file and exit by pressing Ctrl+S followed by Ctrl+X

Now run the below command:

  source ~/.bashrc

1...Using the short cut Ctlr + Alt + T to open terminal

2...Execute the below command:

echo export JAVA_HOME='$(readlink -f /usr/bin/javac | sed "s:/bin/javac::")' | sudo tee /etc/profile.d/jdk_home.sh > /dev/null

3...(Recommended) Restart your VM / computer. You can use source /etc/source if don't want to restart computer

4...Using the short cut Ctlr + Alt + T to open terminal

5...Verified JAVA_HOME installment with

echo $JAVA_HOME

---

One-liner copy from flob, credit to them

This is a very simple script to solve the problem

export JAVA_HOME_BIN=`which java`
export JAVA_HOME_DIR=`dirname $JAVA_HOME_BIN`
export JAVA_HOME=`dirname $JAVA_HOME_DIR`

And for testing:

echo $JAVA_HOME

Posting as answer, as I don't have the privilege to comment.

Point to note: follow the accepted answer posted by "That Dave Guy".

After setting the variables, make sure you set the appropriate permissions to the java directory where it's installed.

chmod -R 755 /usr/java

All operational steps(finding java, parent dir, editing file,...) one solution

zFileProfile="/etc/profile"
zJavaHomePath=$(readlink -ze $(which java) | xargs -0 dirname | xargs -0 dirname)
echo $zJavaHomePath

echo "export JAVA_HOME=\"${zJavaHomePath}\"" >> $zFileProfile
echo "export PATH=\$PATH:\$JAVA_HOME/bin" >> $zFileProfile

Result:

# tail -2 $zFileProfile
export JAVA_HOME="/usr/lib/jvm/java-11-openjdk-11.0.7.10-1.el8_1.x86_64"
export PATH=$PATH:$JAVA_HOME/bin

Explanation:

1. Let's break the full command into pieces

   $(readlink -ze $(which java) | xargs -0 dirname | xargs -0 dirname)

2. Find java path from java command

   $(which java)

   "/usr/bin/java"

3. Get relative path from symbolic path

   readlink -ze /usr/bin/java

   "/usr/lib/jvm/java-11-openjdk-11.0.7.10-1.el8_1.x86_64/bin/java"

4. Get parent path of /usr/lib/jvm/java-11-openjdk-11.0.7.10-1.el8_1.x86_64/bin/java

   readlink -ze /usr/bin/java | xargs -0 dirname

   "/usr/lib/jvm/java-11-openjdk-11.0.7.10-1.el8_1.x86_64/bin"

5. Get parent path of /usr/lib/jvm/java-11-openjdk-11.0.7.10-1.el8_1.x86_64/bin/

   readlink -ze /usr/bin/java | xargs -0 dirname | xargs -0 dirname

   "/usr/lib/jvm/java-11-openjdk-11.0.7.10-1.el8_1.x86_64"

Step 1 - check the current java version by "echo $JAVA_HOME"

Step 2 - vim /etc/profile

Step 3 - At the end of file you will find export JAVA_HOME, we need to provide the new path here, make sure that it is not relative.

Step 4 - Save and exit :wq

Step 5 - "source /etc/profile/", this would execute the change

Step 6 - Again do a echo $JAVA_HOME - change would have been reflected.

Probably a good idea to source whatever profile you edit to save having to use a fresh login.

either: source /etc/ or . /etc/

Where is whatever profile you edited.

On Linux I add this line to my ~/.profile:

export JAVA_HOME=$(readlink -ze /usr/bin/javac | xargs -0 dirname -z | xargs -0 dirname)

While we are up to setting JAVA_HOME, let me share some benefits of setting JAVA_HOME or any other environment variable:

1. It's easy to upgrade JDK without affecting your application startup and config file which points to JAVA_HOME. you just need to download new version and make sure your JAVA_HOME points to new version of Java. This is best benefit of using environment variable or links.

2. JAVA_HOME variable is short and concise instead of full path to JDK installation directory.

3. JAVA_HOME variable is platform independence i.e. if your startup script uses JAVA_HOME then it can run on Windows and UNIX without any modification, you just need to set JAVA_HOME on respective operating system.

Read more: http://javarevisited.blogspot.com/2012/02/how-to-set-javahome-environment-in.html#ixzz4BWmaYIjH

open kafka-run-class.sh with sudo to write

you can find kafka-run-class.sh in your kafka folder : kafka/bin/kafka-run-class.sh

check for these lines

Modify the JAVA variable in the else part to point to the java executable in your java/bin. like JAVA="$JAVA_HOME/java"

In /etc/profile , if you open that will you’ll get to know that IT IS no recommended to write on that file. Instead of that make a script of your commands(suppose test.sh)go to /etc/profile.d folder and Put test.sh there. Every time you instance reboot it’ll be automatically called by /etc/profile.

Use SDKMAN sdkman.io to switch btw. your sdk's.

It sets the JAVA_HOME for you.

Using vim might be a bit difficult for new user. We can use gedit text editor instead.

1. Find /usr/lib/jvm/java-1.x.x-openjdk

2. Enter "gedit /etc/profile" or use "sudo gedit /etc/profile" if logged in as not-privileged

3. Add the following at the end of line:

   export JAVA_HOME="path that you found"

   export PATH=$JAVA_HOME/bin:$PATH

4. Enter "source /etc/profile" in your current shell to apply the changes

I use the line:

export JAVA_HOME=$(readlink -f $(dirname $(readlink -f $(which java) ))/../)

to my ~/.profile so it uses the base of the default java directory at login time. This is for bash.