Maven: JAVA_HOME is not defined correctly

Question

I've installed and configured Maven and Java. I can successfully run

mvn spring-boot:run

But when I run

sudo mvn spring-boot:run

I am getting Maven: JAVA_HOME is not defined correctly

When I do

$ echo $JAVA_HOME
/home/ubuntu/jdk1.8.0_26

Am I missing something here?

Answer 1

You will probably want to edit your sudoers file with sudo visudo, find the line Defaults env_reset and add a line Defaults env_keep = "JAVA_HOME" below it. See below for explanation, details, and alternatives.

Why sudo Is Clearing JAVA_HOME

When you run a command with sudo, by default your environment is not passed intact. Most environment variables are removed, for security, and this is usually desirable. As man sudoers says, in the section on "Command environment":

Since environment variables can influence program behavior, sudoers provides a means to restrict which variables from the user's environment are inherited by the command to be run. There are two distinct ways sudoers can deal with environment variables.

By default, the env_reset option is enabled. This causes commands to be executed with a new, minimal environment. On AIX (and Linux systems without PAM), the environment is initialized with the contents of the /etc/environment file. The new environment contains the TERM, PATH, HOME, MAIL, SHELL, LOGNAME, USER, USERNAME and SUDO_* variables in addition to variables from the invoking process permitted by the env_check and env_keep options. This is effectively a whitelist for environment variables.

If, however, the env_reset option is disabled, any variables not explicitly denied ....

Letting JAVA_HOME Through One Time

One option, if you rarely run mvn spring-boot:run as root and prefer not to change your configuration at all, is simply to pass on the value of JAVA_HOME manually:

sudo JAVA_HOME="$JAVA_HOME" mvn spring-boot:run

When you run that:

1. The shell performs parameter expansion and quote removal, replacing "$JAVA_HOME" with the value (i.e., contents) of JAVA_HOME. If that contains no blank spaces, the quotes are not necessary (their purpose here is to prevent word splitting).
2. sudo is called with three arguments: JAVA_HOME=..., where ... is the value of JAVA_HOME when you ran the command; mvn, and spring-boot:run.
3. sudo recognizes variable=value syntax, and knows to run mvn with JAVA_HOME set to the specified value. (spring-boot:run is passed as the first command-line argument to mvn).

To pass all your environment variables through, you can run sudo -E mvn spring-boot:run, but this is potentially less secure and not ideal because JAVA_HOME is the only variable whose value you need preserved (besides the handful of variables whose values are automatically preserved even with env_reset).

Letting JAVA_HOME Through Every Time

Although you could disable env_reset in your sudoers file, this would pass almost all a user's environment variables through every time sudo is run, and for this reason is not recommended.

Instead, I recommend you edit your sudoers file and add an appropriate env_keep line after the env_reset line.

• Please do not edit /etc/sudoers directly. Instead, you should always use the visudo command for this, which checks to ensure your syntax is correct (preventing the creation of an invalid sudoers file which locks down sudo until fixed).

Run:

sudo visudo

This will use your default command-line text editor. If you want to use a different editor, you can run visudo with it assigned to the VISUAL environment variable. For example:

• sudo VISUAL=nano visudo
• sudo VISUAL=gedit visudo

^{(VISUAL isn't so named after the "vis" in visudo; instead, it's the environment variable for specifying default text editors. You can also use the EDITOR variable, but VISUAL takes priority if set.)}

Running visudo opens up a temporary copy of your sudoers file in a text editor; on exit, changes made to this copy are written to /etc/sudoers.

Find the line that says:

Defaults        env_reset

Add a line just under it, saying:

Defaults        env_keep = "JAVA_HOME"

(If you already have an env_keep line, add JAVA_HOME to the quoted list of allowed variables. The variable names are separated from one another with spaces.)

Save the file and quit the text editor. Now, when users run commands with sudo, the JAVA_HOME environment variable will be preserved.