有些客户需要在VPS安装java/jdk6，但是一个一个下载和编译安装十分话时间，那么，Linux/centos如何YUM安装Java和JDK环境？

首先，我们来看看yum库是否有java安装包

[root@233797 www.ctohome.com]yum -y list java*
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirror.grikare.com
 * extras: centos.mirror.facebook.net
 * rpmforge: ftp-stud.fht-esslingen.de
 * updates: mirror.grikare.com
Excluding Packages in global exclude list
Finished
Available Packages
java-1.4.2-gcj-compat.i386                                                              1.4.2.0-40jpp.115                                                                base  
java-1.4.2-gcj-compat-devel.i386                                                        1.4.2.0-40jpp.115                                                                base  
java-1.4.2-gcj-compat-javadoc.i386                                                      1.4.2.0-40jpp.115                                                                base  
java-1.4.2-gcj-compat-src.i386                                                          1.4.2.0-40jpp.115                                                                base  
java-1.6.0-openjdk.i386                                                                 1:1.6.0.0-1.23.1.9.10.el5_7                                                      updates
java-1.6.0-openjdk-demo.i386                                                            1:1.6.0.0-1.23.1.9.10.el5_7                                                      updates
java-1.6.0-openjdk-devel.i386                                                           1:1.6.0.0-1.23.1.9.10.el5_7                                                      updates
java-1.6.0-openjdk-javadoc.i386                                                         1:1.6.0.0-1.23.1.9.10.el5_7                                                      updates
java-1.6.0-openjdk-src.i386                                                             1:1.6.0.0-1.23.1.9.10.el5_7                                                      updates
java_cup.i386                                                                           1:0.10-0.k.6jpp.1                                                                base  
java_cup-javadoc.i386                                                                   1:0.10-0.k.6jpp.1                                                                base  
java_cup-manual.i386                                                                    1:0.10-0.k.6jpp.1                                                                base  
javacc.i386                                                                             4.0-3jpp.3                                                                       base  
javacc-demo.i386                                                                        4.0-3jpp.3                                                                       base  
javacc-manual.i386                                                                      4.0-3jpp.3     

然后我们安装java1.6.x，怎样使用yum安装java？ 怎么用yum安装jdk？

[root@233797 www.ctohome.com]yum -y install  java-1.6.0-openjdk*

查看yum安装java的结果，安装完成后，执行java -version

[root@233797 www.ctohome.com]java -version
java version "1.6.0_20"
OpenJDK Runtime Environment (IcedTea6 1.9.10) (rhel-1.23.1.9.10.el5_7-i386)
OpenJDK Client VM (build 19.0-b09, mixed mode)

 执行java的时候，遇到错误：

Could not reserve enough space for object heap

Could not create the Java virtual machine.

解决办法：

在ssh下用root执行

export _JAVA_OPTIONS="-Xms32m -Xmx64m -XX:MinHeapFreeRatio=20 -XX:MaxHeapFreeRatio=40 -XX:NewSize=10m -XX:MaxNewSize=10m -XX:SurvivorRatio=6 -XX:TargetSurvivorRatio=80 -XX:+CMSClassUnloadingEnabled -XX:+CMSPermGenSweepingEnabled"

 还有错误的话，请参考
http://forums.vpslink.com/linux/1327-java-could-not-reserve-enough-space-object-heap.html

http://forum.openvz.org/index.php?t=msg&goto=7061