[linux] Make $JAVA_HOME easily changable in Ubuntu

In Ubuntu, I'd like to switch my JAVA_HOME environment variable back and forth between Java 5 and 6.

I open a terminal and type in the following to set the JAVA_HOME environment variable:

export JAVA_HOME=/usr/lib/jvm/java-1.5.0-sun

And in that same terminal window, I type the following to check that the environment variable has been updated:

echo $JAVA_HOME

And I see /usr/lib/jvm/java-1.5.0-sun which is what I'm expecting to see. In addition, I modify ~/.profile and set the JAVA_HOME environment variable to /usr/lib/jvm/java-1.5.0-sun.

And now for the problem--when I open a new terminal window and I check my JAVA_HOME environment variable by typing in echo $JAVA_HOME I see that my JAVA_HOME environment variable has been reverted back to Java 6. When I reboot my machine (or log out and back in, I suppose) the JAVA_HOME environment variable is set to Java 5 (presumably because of the modification I made in my ~/.profile).

Is there a way around this so that I can change my JAVA_HOME environment without having to log out and back in (AND make that environment variable change stick in all new terminal windows)?

Try these steps.

--We are going to edit "etc\profile". The environment variables are to be input at the bottom of the file. Since Ubuntu does not give access to root folder, we will have to use a few commands in the terminal

Step1: Start Terminal. Type in command: gksudo gedit /etc/profile

Step2: The profile text file will open. Enter the environment variables at the bottom of the page........... Eg: export JAVA_HOME=/home/alex/jdk1.6.0_22/bin/java

export PATH=/home/alex/jdk1.6.0_22/bin:$PATH

step3: save and close the file. Check if the environment variables are set by using echo command........ Eg echo $PATH

Take a look at bash(1), you need a login shell to pickup the ~/.profile, i.e. the -l option.

I know this is a long cold question, but it comes up every time there is a new or recent major Java release. Now this would easily apply to 6 and 7 swapping.

I have done this in the past with update-java-alternatives: http://manpages.ubuntu.com/manpages/hardy/man8/update-java-alternatives.8.html

Traditionally, if you only want to change the variable in your terminal windows, set it in .bashrc file, which is sourced each time a new terminal is opened. .profile file is not sourced each time you open a new terminal.

See the difference between .profile and .bashrc in question: What's the difference between .bashrc, .bash_profile, and .environment?

.bashrc should solve your problem. However, it is not the proper solution since you are using Ubuntu. See the relevant Ubuntu help page "Session-wide environment variables". Thus, no wonder that .profile does not work for you. I use Ubuntu 12.04 and xfce. I set up my .profile and it is simply not taking effect even if I log out and in. Similar experience here. So you may have to use .pam_environment file and totally forget about .profile, and .bashrc. And NOTE that .pam_environment is not a script file.

You need to put variable definition in the ~/.bashrc file.

From bash man page:

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.

After making changes to .profile, you need to execute the file, in order for the changes to take effect.

root@masternode# . ~/.profile

Once this is done, the echo command will work.

This will probably solve your problem: https://help.ubuntu.com/community/EnvironmentVariables

Session-wide environment variables

In order to set environment variables in a way that affects a particular user's environment, one should not place commands to set their values in particular shell script files in the user's home directory, but use:

~/.pam_environment - This file is specifically meant for setting a user's environment. It is not a script file, but rather consists of assignment expressions, one per line.

Not recommended:

~/.profile - This is probably the best file for placing environment variable assignments in, since it gets executed automatically by the DisplayManager during the startup process desktop session as well as by the login shell when one logs-in from the textual console.