Find Java_Home and Set It on Rhel

Find JAVA_HOME and set it on RHEL

First, try echo $JAVA_HOME from the command line. Since java is on your path already, JAVA_HOME may be set.

What is the best way to figure out the installation directory of my java installation

Running the command which java will point you to where java is installed.

and then set JAVA_HOME

You can edit ~/.bashrc, ~/.bash_profile, or /etc/profile to set JAVA_HOME. Setting it in ~/etc/profile will set it system wide, and this is probably not what you want. Say for the sake of example the output of which java is /opt/jdk_1.7.0_25, then you'd just add export JAVA_HOME=/opt/jdk_1.7.0_25 to ~/.bashrc or ~/.bash_profile and then run source ~/.bashrc (or source ~/.bash_profile if you set it there).

Note that in this case, java is on the PATH but in some cases you'd need to add export PATH=$PATH:$JAVA_HOME/bin to add the JAVA_HOME variable to the PATH.

Cannot find JAVA_HOME in Red Hat Server

Try the file /etc/bash.bashrc, sometimes it is also used to initialise bash. If not, then try to find the word JAVA_HOME inside the files in /etc with grep -r BASH_HOME /etc

UPDATE

From man bash:

When bash is invoked as an interactive login shell, or as a non-interactive shell with the --login option, it first reads and executes commands from the file /etc/profile, if that file exists. After reading that file, it looks for ~/.bash_profile, ~/.bash_login, and ~/.profile, in that order, and reads and executes
commands from the first one that exists and is readable.

and also:

When an interactive shell that is not a login shell is started, bash reads and executes commands from /etc/bash.bashrc and ~/.bashrc, if these files exist.

So the only file that you haven't had a look at is ~/bash_login.

Probably JAVA_HOME is not in any of these files and what happens is that one of these files call another script, in that case, you'll have to read line by line if one of these scripts is "loading" more scripts from other places

How to set JAVA_HOME in Linux for all users

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

JAVA_HOME directory in Linux

echo $JAVA_HOME will print the value if it's set. However, if you didn't set it manually in your startup scripts, it probably isn't set.

If you try which java and it doesn't find anything, Java may not be installed on your machine, or at least isn't in your path. Depending on which Linux distribution you have and whether or not you have root access, you can go to http://www.java.com to download the version you need. Then, you can set JAVA_HOME to point to this directory. Remember, that this is just a convention and shouldn't be used to determine if java is installed or not.

JAVA_HOME and PATH are set but java -version still shows the old one

While it looks like your setup is correct, there are a few things to check:

1. The output of env - specifically PATH.
2. command -v java tells you what?
3. Is there a java executable in $JAVA_HOME\bin and does it have the execute bit set? If not chmod a+x java it.

I trust you have source'd your .profile after adding/changing the JAVA_HOME and PATH?

Also, you can help yourself in future maintenance of your JDK installation by writing this instead:

export JAVA_HOME=/home/aqeel/development/jdk/jdk1.6.0_35
export PATH=$JAVA_HOME/bin:$PATH

Then you only need to update one env variable when you setup the JDK installation.

Finally, you may need to run hash -r to clear the Bash program cache. Other shells may need a similar command.

Cheers,

Unable to find JAVA_HOME

Type which java and you will probably see (at least after you have followed all the symlinks) that the Java executable is taken from somewhere else than your newly set JAVA_HOME. You need to create the appropriate symlinks to version 1.8, too, like this:

ln -s /your/path/to/v18/bin/java /usr/bin/java

Be aware that existing applications might use the 1.7 Java version and you might break them when you set /usr/bin/java (or whatever path the which command showed you) to the 1.8 version.

Fyi, JAVA_HOME is not meant to be used by your shell to locate the Java command. It is to be used by other software that require Java to know where to find it.

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