centos view the Java installation path, configure the environment variables

installation path

[hadoop@192 /]$ which java
/bin/java
[hadoop@192 /]$ ls -lrt /bin/java
lrwxrwxrwx. 1 root root 22 4月  17 06:25 /bin/java -> /etc/alternatives/java
[hadoop@192 /]$ ls -lrt /etc/alternatives/java
lrwxrwxrwx. 1 root root 72 4月  17 06:25 /etc/alternatives/java -> /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.131-11.b12.el7.x86_64/jre/bin/java
[hadoop@192 /]$ 

rpm -ql java-1.7.0-openjdk-devel | grep '/bin/javac'

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Configure the environment variables (Global)

Placed JAVA_HOME

1. Open the configuration file environment variables

vi /etc/profile.d/java.sh

2. Add the following configuration:

export JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.181-3.b13.el7_5.x86_64
export JRE_HOME=$JAVA_HOME/jre
export CLASSPATH=$JAVA_HOME/lib:$JRE_HOME/lib:$CLASSPATH
export PATH=$JAVA_HOME/bin:$JRE_HOME/bin:$PATH

: Wq save and exit.

3. Let configuration to take effect

source   /etc/profile.d/java.sh

4. Test Configuration

echo $JAVA_HOME

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• CentOS are three ways to add environment variables

• JAVA_HOME arrangement

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Supplementary: / etc / profile and the difference between /etc/profile.d

1. Both are set environment variables
2. /etc/profile.d/ than / etc / profile good maintenance, do not want to delete /etc/profile.d/ under what variables corresponding to the shell script, do not like / etc / profile need to change the file
   below to the jdk installation Case Study

vi /etc/profile.d/java.sh Enter the following in a new java.sh in:

#set java environment
 
JAVA_HOME=/var/mysoft/jdk1.7.0_80
PATH=$JAVA_HOME/bin:$PATH
export JAVA_HOME PATH

Save and exit, and then assign permissions to java.sh: chmod 755 /etc/profile.d/java.sh

echo $JAVA_HOME