问题：

I am trying to install apache maven 3 in Ubuntu 12.04 lts. What I did was open the terminal then I typed the following commands

• export M2_HOME=/usr/local/apache-maven/apache-maven-3.0.5 [Then pressed Enter]
• export M2=$M2_HOME/bin [Then pressed Enter]
• export PATH=$M2:$PATH [Then pressed Enter]

After that I typed

mvn --version

and it displayed all the necessary information but after closing the terminal, again I typed the command mvn --version

The program ‘mvn‘ can be found in the following packages:
 * maven
 * maven2
Try sudo apt-get install <selected-page>

解决方式例如以下http://askubuntu.com/questions/310059/ubuntu-adding-path-environment-variables

问题是在环境里面加入了PATH，可是须要

$source /etc/environment

然后mvn --vsersion

xx@xxx:/usr/local$ mvn --version
Apache Maven 3.2.2 (45f7c06d68e745d05611f7fd14efb6594181933e; 2014-06-17T21:51:42+08:00)
Maven home: /usr/local/apache-maven-3.2.2
Java version: 1.7.0_55, vendor: Oracle Corporation
Java home: /usr/lib/jvm/java-7-openjdk-amd64/jre
Default locale: en_US, platform encoding: UTF-8
OS name: "linux", version: "3.13.0-29-generic", arch: "amd64", family: "unix"