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Help identify confusing way Maven is running with no M2_HOME?

rated 0 times [ 1] [ 0] / answers: 1 / hits: 2430 / 1 Year ago, thu, march 16, 2023, 10:07:11

I am running Ubuntu 12.04 and am a Java developer who has recently moved off his desktop and started working on a new laptop. I have a few build issues and am investigating my install of Maven.

I got some help setting up my laptop and find the following Maven configuration confusing. I have Maven installed (by a peer I assume) and running but have no M2_HOME. I would have thought it would be a requirement.

The following is my output when I run mvn --version

Apache Maven 3.0.4

Maven home: /usr/share/maven

Java version: 1.7.0_51, vendor: Oracle Corporation

Java home: /usr/lib/jvm/java-7-openjdk-amd64/jre

Default locale: en_GB, platform encoding: UTF-8 

OS name: "linux", version: "3.5.0-23-generic", arch: "amd64", family: "unix"

None of the following give me anything: printenv | grep "maven", printenv | grep "mvn", printenv | grep "M2".

There is nothing special in ~/.profile or /etc/environment related to Maven.

Can you provide any clues/direction as to why mvn --version in the console gives output?

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rcraftemur

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3 Years ago

answered 1 Year ago erettor · Accepted Answer

When you do not understand something you have to investigate why it works the way it works... What you just did. And it is great!

In the case of Maven on Linux/Ubuntu you find confusing the locations where the software is installed... OK. But you have to get used... That is the way it works.

Maybe you are used to install maven yourselves and in it case you have the control of the location of the installation and you can even use M2_HOME. I will come back later on M2_HOME.

I did the same researches and for me it is not confusing at all... But of course the locations could be unexpected for some people...

I have installed the package maven2 to do the same investigations...

rudy@rudy-Inspiron-530:~$ sudo apt-get install maven2 (lot of output that was discarded)

rudy@rudy-Inspiron-530:~$ whereis mvn

mvn: /usr/bin/mvn /usr/bin/X11/mvn /usr/share/man/man1/mvn.1.gz

rudy@rudy-Inspiron-530:~$ ls -l /usr/bin/mvn

lrwxrwxrwx 1 root root 21 fév 16 08:23 /usr/bin/mvn -> /etc/alternatives/mvn

rudy@rudy-Inspiron-530:~$ ls -l /usr/bin/X11/mvn

lrwxrwxrwx 1 root root 21 fév 16 08:23 /usr/bin/X11/mvn -> /etc/alternatives/mvn

rudy@rudy-Inspiron-530:~$ ls -l /etc/alternatives/mvn

lrwxrwxrwx 1 root root 25 fév 16 08:23 /etc/alternatives/mvn -> /usr/share/maven2/bin/mvn

rudy@rudy-Inspiron-530:~$ ls -l /usr/share/maven2/bin/mvn

-rwxr-xr-x 1 root root 6331 jun 25  2013 /usr/share/maven2/bin/mvn

There are soft links that are used. I see in the path /usr/bin/mvn and /usr/bin/X11/mvn. Then /usr/bin/mvn, /usr/bin/X11/mvn and /etc/alternatives/mvn are ALL soft links.

There are several levels and of course it can confuse you...

The real thing is in /usr/share/maven2/bin/mvn.

rudy@rudy-Inspiron-530:/usr/bin$ file /usr/share/maven2/bin/mvn

/usr/share/maven2/bin/mvn: POSIX shell script, ASCII text executable

The command 'file' returns what thing you have to deal with...

In the case of /usr/share/maven2/bin/mvn. It is shell script !

You made the assumption that JAVA_HOME and M2_HOME and ... must be initialized and it is a false assumption... Those variables can help you and some other softwares to use a specific version of softwares. Some softwares does not even work without some of these variables... But when you are in a terminal (and you use the packages) you don't need those variables ! Everything will work without.