今天问题还挺多，在VMware上安装Btrace时遇到的，Btrace需要读服务器的JAVA_HOME，当时我配置的是JAVA_HOME=/usr(我以为java命令所在的目录就是JAVA_HOME，真是二的可以)，怎么起不来，报错如下：
Caused by: java.lang.ClassNotFoundException:com.sun.source.util.TaskListener，
询问了开发以后，开发告诉我这是jdk里面的类，应该是你的JAVA_HOME不对。Google了一下，确实是这个问题。
到服务器查了一下，如下
$ rpm -qa |grep jdk
java-1.8.0-openjdk-1.8.0.91-0.b14.el6_7.x86_64
java-1.8.0-openjdk-headless-1.8.0.91-0.b14.el6_7.x86_64
java-1.8.0-openjdk-devel-1.8.0.91-0.b14.el6_7.x86_64
$ rpm -qljava-1.8.0-openjdk-1.8.0.91-0.b14.el6_7.x86_64
/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.91-0.b14.el6_7.x86_64/jre/bin/policytool
/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.91-0.b14.el6_7.x86_64/jre/lib/amd64/libawt_xawt.so
/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.91-0.b14.el6_7.x86_64/jre/lib/amd64/libjawt.so
/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.91-0.b14.el6_7.x86_64/jre/lib/amd64/libjsoundalsa.so
/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.91-0.b14.el6_7.x86_64/jre/lib/amd64/libsplashscreen.so
/usr/share/applications/java-1.8.0-openjdk-1.8.0.91-0.b14.el6_7.x86_64-policytool.desktop
/usr/share/icons/hicolor/16x16/apps/java-1.8.0.png
/usr/share/icons/hicolor/24x24/apps/java-1.8.0.png
/usr/share/icons/hicolor/32x32/apps/java-1.8.0.png
/usr/share/icons/hicolor/48x48/apps/java-1.8.0.png
$ cd /usr/lib/jvm
$ ll
总用量 4
lrwxrwxrwx. 1 root root 26 5月 17 16:59 java-> /etc/alternatives/java_sdk
lrwxrwxrwx. 1 root root 32 5月 17 16:59java-1.8.0 -> /etc/alternatives/java_sdk_1.8.0
drwxr-xr-x. 7 root root 4096 5月 1716:59 java-1.8.0-openjdk-1.8.0.91-0.b14.el6_7.x86_64
lrwxrwxrwx. 1 root root 46 5月 17 16:59java-1.8.0-openjdk.x86_64 -> java-1.8.0-openjdk-1.8.0.91-0.b14.el6_7.x86_64
lrwxrwxrwx. 1 root root 34 5月 17 16:59java-openjdk -> /etc/alternatives/java_sdk_openjdk
lrwxrwxrwx. 1 root root 21 5月 17 16:54 jre ->/etc/alternatives/jre
lrwxrwxrwx. 1 root root 27 5月 17 16:54jre-1.8.0 -> /etc/alternatives/jre_1.8.0
lrwxrwxrwx. 1 root root 50 5月 17 16:54jre-1.8.0-openjdk-1.8.0.91-0.b14.el6_7.x86_64 ->java-1.8.0-openjdk-1.8.0.91-0.b14.el6_7.x86_64/jre
lrwxrwxrwx. 1 root root 50 5月 17 16:54jre-1.8.0-openjdk.x86_64 ->java-1.8.0-openjdk-1.8.0.91-0.b14.el6_7.x86_64/jre
lrwxrwxrwx. 1 root root 29 5月 17 16:54jre-openjdk -> /etc/alternatives/jre_openjdk
o(∩_∩)o ，找到了，JAVA_HOME是/usr/lib/jvm/java。